Power management method, power management system, and power supply apparatus

ABSTRACT

A power management method includes: receiving a surplus power value, indicating an amount of surplus power; receiving an inquiry regarding a power supply using the surplus power in a first time period; and issuing, in accordance with the inquiry, first power identification information in association with an accumulated value of the amount of surplus power corresponding to the first time period, the first power identification information allowing a power supply apparatus to supply power using the surplus power corresponding to the first time period. When a first power supply request associated with the first power identification information and requesting a power supply to a first load is received, the power supply apparatus is caused to supply an amount of power equal to or smaller than the accumulated value of the amount of surplus power, to the first load, as first power that does not cause a fee charging process.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. application Ser.No. 14/924,713, filed Oct. 28, 2015, which claims priority to JapanesePatent Application No. 2015-148150, filed Jul. 27, 2015, and2014-230148, filed Nov. 12, 2014, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a power management method, a powermanagement system, and a power supply apparatus.

2. Description of the Related Art

Power generated using solar energy and the like are currently consumedby load apparatuses or supplied to a power system.

An apparatus that supplies power from a vehicle to power equipmentoutside the vehicle using a storage battery mounted on the vehicle andthen supplies an amount of power corresponding to the amount of theaforementioned power from the power equipment to the vehicle has beendisclosed (refer to Japanese Unexamined Patent Application PublicationNo. 2013-102673).

SUMMARY

In the power management system in an example of the related art,however, surplus power is always sold, and it is difficult for users tomake wider use of surplus power.

One nonlimiting and exemplary embodiment provides a power managementmethod by which it is possible to make wider use of surplus power.

In one general aspect, the techniques disclosed here feature a powermanagement method used in a power management system including a powergeneration apparatus corresponding to first user identificationinformation, a first load apparatus used by a user corresponding to thefirst user identification information, and a power supply apparatuscapable of supplying power to the first load apparatus and installed ina place different from a place where the power generation apparatus isinstalled. The method includes receiving, from a meter that measuresamount of surplus power, which is, in power generated by the powergeneration apparatus, power supplied from the power generation apparatusto a power system, a surplus power value indicating the amount ofsurplus power, receiving, from a first communication terminal used bythe user corresponding to the first user identification information, aninquiry about power supply in which the surplus power is used in a firsttime period that lasts a certain unit time, the inquiry being associatedwith the first user identification information, issuing, in accordancewith the inquiry, first power identification information for validatingpower supply performed by the power supply apparatus using the surpluspower corresponding to the first time period for an accumulated value ofthe amount of surplus power corresponding to the first time period,transmitting the first power identification information and theaccumulated value of the amount of surplus power corresponding to thefirst time period to the first communication terminal, and causing thepower supply apparatus that has received a first power supply request,which is associated with the first power identification information,indicating that power is to be supplied to the first load apparatus tosupply an amount of first power equal to or smaller than the amount ofsurplus power to the first load apparatus as power that does not cause acharging process.

The power management method in the present disclosure makes it possibleto make wider use of surplus power.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a recording medium such as a computer-readable compact discread-only memory (CD-ROM), or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of the configuration of a power management systemaccording to a first embodiment;

FIG. 2 is a block diagram illustrating the configuration of the powermanagement system according to the first embodiment;

FIG. 3 is a schematic diagram specifically illustrating a part of thepower management system according to the first embodiment including auser's home;

FIG. 4 is a block diagram illustrating specific function blocks of apower management apparatus according to the first embodiment;

FIG. 5 is a diagram illustrating a surplus power information tableaccording to the first embodiment;

FIG. 6 is a diagram illustrating a power identifier (ID) management ableaccording to the first embodiment;

FIG. 7 is a diagram illustrating a surplus power use information tableaccording to the first embodiment;

FIG. 8 is a diagram illustrating a power information management tableaccording to the first embodiment;

FIG. 9 is a diagram illustrating a power supply apparatus useinformation table according to the first embodiment;

FIG. 10 is a diagram illustrating surplus power according to the firstembodiment;

FIG. 11 is a diagram illustrating an inquiry about the possibility ofpower supply and a response to the inquiry according to the firstembodiment;

FIG. 12 is a flowchart illustrating an overall process performed by thepower management system according to the first embodiment;

FIG. 13 is a sequence diagram illustrating transmission of informationin the power management system according to the first embodiment from aprocess for inquiring about the possibility of power supply to a processfor reporting power supply;

FIG. 14 is a sequence diagram illustrating transmission of informationin the power management system according to a modification of the firstembodiment from the process for inquiring about the possibility of powersupply to the process for reporting power supply;

FIG. 15 is a sequence diagram illustrating transmission of informationin the power management system according to the first embodiment duringa charging process;

FIG. 16 is a flowchart illustrating a process performed by the powermanagement apparatus according to the first embodiment;

FIG. 17 is a first flowchart illustrating a process for identifyingsurplus power performed by a surplus power identification unit accordingto the first embodiment;

FIG. 18 is a second flowchart illustrating the process for identifyingsurplus power performed by the power management apparatus according tothe first embodiment;

FIG. 19 is a flowchart illustrating a process for inquiring about apower ID performed by the power management apparatus according to thefirst embodiment;

FIG. 20 is a flowchart illustrating a process for updating the amount ofsurplus power used performed by the power management apparatus accordingto the first embodiment;

FIG. 21 is a flowchart illustrating a process for calculating anelectricity bill in a settlement process according to the firstembodiment;

FIG. 22 is an overview of the configuration of a power management systemaccording to a second embodiment;

FIG. 23 is a block diagram illustrating the configuration of the powermanagement system according to the second embodiment;

FIG. 24 is a first sequence diagram illustrating transmission ofinformation in the power management system according to the secondembodiment;

FIG. 25 is a first sequence diagram illustrating transmission ofinformation in a power management system according to a thirdembodiment;

FIG. 26 is a second sequence diagram illustrating the transmission ofinformation in the power management system according to the thirdembodiment;

FIG. 27 is a third sequence diagram illustrating the transmission ofinformation in the power management system according to the thirdembodiment;

FIG. 28 is a block diagram illustrating another example of theconfiguration of the power management system according to eachembodiment; and

FIG. 29 is a flowchart illustrating a power management method in thepower management system according to each embodiment.

DETAILED DESCRIPTION Underlying Knowledge Forming Basis of the PresentDisclosure

The present inventor has found that the following problem occurs in thetransmission of power described in “Description of the Related Art”.

After the power liberalization in Japan in 2016, consumers will be ableto select any power retailers. Because regulations on electricity billswill be removed, retailers need to propose attractive contracts or rateplans that are useful to consumers.

Retailers will make contracts not only with conventional power supplypoints (households and buildings) but also with individuals. Inaddition, a contract will be possible that specifies that if a consumerreceives power with a device (a mobile device, an electric vehicle (EV),or the like) at a place other than the consumer's home (e.g., a publiccharging spot), the consumer pays for the power with a singletransaction along with power consumed in the consumer's home.

On the other hand, power generated by consumers using renewable energysuch as solar energy is now purchased by power companies for premiumprices in order to tactically popularize such a type of powergeneration. As solar power generation equipment becomes popular,however, the prices are falling. In the future, the prices can be equalto or lower than those of grid power.

In such a situation, consumers might not sell surplus power caused byhome solar power systems to power companies but might want to use thesurplus power themselves or provide (or present) the surplus power forothers such as friends or relatives.

In the power management system in the example of the related art,however, surplus power is always sold, and it is difficult for users tomake wider use of surplus power.

The present disclosure provides a power management system capable ofmaking wider use of surplus power.

In order to solve such a problem, a power management method according toan aspect of the present disclosure is a power management method used ina power management system including a power generation apparatuscorresponding to first user identification information, a first loadapparatus used by a user corresponding to the first user identificationinformation, and a power supply apparatus capable of supplying power tothe first load apparatus and installed in a place different from a placewhere the power generation apparatus is installed. The method includesreceiving, from a meter that measures amount of surplus power, which is,in power generated by the power generation apparatus, power suppliedfrom the power generation apparatus to a power system, a surplus powervalue indicating the amount of surplus power, receiving, from a firstcommunication terminal used by the user corresponding to the first useridentification information, an inquiry about power supply in which thesurplus power is used in a first time period that lasts a certain unittime, the inquiry being associated with the first user identificationinformation, issuing, in accordance with the inquiry, first poweridentification information for validating power supply performed by thepower supply apparatus using the surplus power corresponding to thefirst time period for an accumulated value of the amount of surpluspower corresponding to the first time period, transmitting the firstpower identification information and the accumulated value of the amountof surplus power corresponding to the first time period to the firstcommunication terminal, and causing the power supply apparatus that hasreceived a first power supply request, which is associated with thefirst power identification information, indicating that power is to besupplied to the first load apparatus to supply an amount of first powerequal to or smaller than the amount of surplus power to the first loadapparatus as power that does not cause a charging process.

According to the above aspect, in the power management system, thesurplus power caused in a home of a user (consumer) is supplied to thepower system (reverse flow) whereas the power system supplies power at aplace different from the user's home. As a result, the user can not onlysell the surplus power but also receive an amount of power correspondingto the amount of surplus power at another place. The power managementsystem can thus make wider use of surplus power. In other words, sincethe user consumes the surplus power at a place different from his/herhome, the power management system can balance the amount of powerconsumed and the amount of power supplied with each other moreappropriately in the first time period.

The first power supply request may be, for example, input from the firstcommunication terminal to the power supply apparatus.

According to the above aspect, in the power management system, the powersupply apparatus receives the first power supply request from the firstcommunication terminal. The power management system can thereforereceive the first power supply request more securely using the firstcommunication terminal.

The surplus power value may be, for example, periodically received fromthe meter. After the inquiry is received, surplus power values may beaccumulated from a start of the first time period including a receptiontime, which is a time at which the inquiry has been received, to thereception time to generate an accumulated value of the amount of surpluspower corresponding to the first time period.

According to the above aspect, in the power management system, theaccumulated value of the amount of surplus power can be specificallycalculated using the surplus power value periodically transmitted fromthe meter.

After the inquiry is received, for example, the meter may be requestedto output surplus power values corresponding to the first time periodincluding a reception time, which is a time at which the inquiry hasbeen received. After the surplus power values corresponding to the firsttime period are received from the meter, the surplus power valuescorresponding to the first time period may be accumulated to generate anaccumulated value of the amount of surplus power corresponding to thefirst time period.

According to the above aspect, in the power management system, theaccumulated value of the amount of surplus power can be specificallycalculated using the surplus power value periodically transmitted fromthe meter.

The first power supply request may include, for example, a valueindicating amount of power to be supplied to the first load apparatus.

According to the above aspect, since the power management apparatusreceives the power supply request including the amount of power to besupplied in the power management system, the power management apparatuscan determine whether an amount of power corresponding the amount ofpower included in the power supply request can be supplied.

If the accumulated value of the amount of surplus power corresponding tothe first time period is equal to or smaller than a certain minimumvalue, for example, control may be performed such that the first poweridentification information is not issued or associated with theaccumulated value of the amount of surplus power corresponding to thefirst time period.

According to the above aspect, if the amount of power that can besupplied from the power supply apparatus is equal to or smaller than thecertain minimum value, the power management apparatus can prohibit thepower supply apparatus from supply power by controlling the issuance ofthe power ID.

If the accumulated value of the amount of surplus power corresponding tothe first time period is equal to or smaller than a certain minimumvalue, for example, control may be performed such that the first poweridentification information and the accumulated value are not transmittedto the first communication terminal in accordance with the inquiry.

According to the above aspect, if the amount of power that can besupplied from the power supply apparatus is equal to or smaller than thecertain minimum value, the power management apparatus can prohibit thepower supply apparatus from supplying power by controlling the issuanceof the power ID.

If the accumulated value of the amount of surplus power corresponding tothe first time period is equal to or smaller than a certain minimumvalue, for example, control may be performed such that a notificationindicating that the accumulated value of the amount of surplus powercorresponding to the first time period is equal to or smaller than thecertain minimum value is transmitted to the first communication terminalin accordance with the inquiry.

According to the above aspect, the power management apparatus can notifythe user that the amount of power that can be supplied from the powersupply apparatus is equal to or smaller than the certain minimum valueby transmitting the notification to the first communication terminal.

The method further may include, for example, receiving, from the powersupply apparatus, an inquiry request including a value indicating amountof power to be supplied to the first load apparatus, and outputting, ifthe value included in the inquiry request exceeds the accumulated valueof the amount of surplus power corresponding to the first time period,an instruction to prohibit the power supply apparatus from supplyingpower to the first load apparatus.

According to the above aspect, the power management apparatus canprohibit the power supply apparatus from supplying power using theinstruction to prohibit the power supply apparatus from supplying anamount of power larger than the amount of surplus power.

The method further may include, for example, receiving, from the powersupply apparatus, an inquiry request including a value indicating amountof power to be supplied to the first load apparatus, and causing, if thevalue included in the inquiry request exceeds the accumulated value ofthe amount of surplus power corresponding to the first time period, thepower generation apparatus to supply an amount of first powercorresponding to the accumulated value of the amount of surplus powercorresponding to the first time period to the first load apparatus aspower that does not cause a charging process.

According to the above aspect, the power management apparatus can supplyan amount of power equal to or smaller than the amount of surplus powerin response to the request to supply an amount of power larger than theamount of surplus power.

After the first time period ends, for example, management may beperformed such that power supply performed by the power supply apparatususing the surplus power corresponding to the first time period on thebasis of the first power identification information is invalidated.

According to the above aspect, the power management system can performpower supply based on the first identification information only in thefirst time period. The power management system can therefore make wideruse of surplus power without significantly disrupting powersupply-demand balance in a transmission and distribution network.

The power management system further may include, for example, a secondload apparatus, which is different from the first load apparatus andinstalled in the same building as the power generation apparatus. Powerobtained by subtracting power used by the second load apparatus from thepower generated by the power generation apparatus is determined as thesurplus power.

According to the above aspect, the power management apparatus canspecifically calculate the amount of surplus power using the amount ofpower generated by the power generation apparatus and the amount ofpower consumed by the second load apparatus.

If the power generation apparatus has not obtained the first poweridentification information, for example, the power supply apparatus maysupply second power that causes a charging process to the first loadapparatus.

According to the above aspect, in the power management system, the powersupply apparatus can supply either power that causes a charging processor power that does not cause a charging process on the basis of whetherthe first power identification information is present. Since the powermanagement system performs management such that the surplus poweroffsets the power supplied from the power supply apparatus, the userneed not pay for the power supplied from the power supply apparatus. Theuser can therefore make wider use of surplus power without paying extramoney.

The power supply apparatus may include, for example, a receiver used fora process for paying money for supplied power. The method may furtherinclude performing control, if the second power has been supplied, suchthat the receiver accepts the process for paying money, and control, ifthe first power has been supplied, such that the receiver prohibits theprocess for paying money.

According to the above aspect, the power management system determineswhether to accept the process for paying money in accordance withwhether the supplied power causes a charging process. The powermanagement system can therefore appropriately perform the process forpaying money for the supplied power.

The method further may include, for example, performing a process forcalculating a price corresponding to the amount of surplus power. If thepower supply apparatus has supplied the first power to the first loadapparatus, a process for calculating a price corresponding to amount ofpower obtained by subtracting amount of first power supplied from theaccumulated value of the amount of surplus power may be performed in thecalculation process.

According to the above aspect, the power management system provides, forthe user, the price corresponding to the amount of power obtained bysubtracting the amount of power supplied from the power supply apparatusfrom the price corresponding to the amount of surplus power. The usercan therefore make wider use of surplus power without paying extramoney.

The first communication terminal may transmit, for example, the firstpower identification information and the accumulated value of the amountof surplus power corresponding to the first time period to a secondcommunication terminal used by a user corresponding to second useridentification information different from the first user identificationinformation. If the second communication terminal has transmitted, tothe power supply apparatus, a second power supply request indicatingthat power is to be supplied to a third load apparatus, which is used bythe user corresponding to the second user identification information anddifferent from the first load apparatus, the power supply apparatus maysupply an amount of first power equal to or smaller than the amount ofsurplus power to the third load apparatus as power that does not cause acharging process.

According to the above aspect, in the power management system, thesurplus power caused in a home of a first user (the user correspondingto the first user identification information) is supplied to the powersystem (reverse flow) whereas a second user (the user corresponding tothe second user identification information) that does not own a powergeneration apparatus can receive power from the power system. Even userswho do not own a power generation apparatus can therefore use surpluspower.

The first power identification information and temporary second poweridentification information different from the first power identificationinformation may be, for example, associated with the accumulated valueof the amount of surplus power corresponding to the first time periodand issued in accordance with the inquiry. The first poweridentification information, the second power identification information,and the accumulated value of the amount of surplus power correspondingto the first time period may be transmitted to the first communicationterminal. The first communication terminal may transmit the second poweridentification information and the accumulated value of the amount ofsurplus power to a second communication terminal used by a usercorresponding to second user identification information different fromthe first user identification information. The second communicationterminal may transmit, to the power supply apparatus, a second powersupply request indicating that power is to be supplied to a second loadapparatus, which is used by the user corresponding to the second useridentification information and different from the first load apparatus.If the power supply apparatus has supplied an amount of first powerequal to or smaller than the amount of surplus power to the second loadapparatus as power that does not cause a charging process, the firstpower may be prohibited from being supplied to the first load apparatus.

According to the above aspect, in the power management system, thesecond user is allowed to supply power to his/her load apparatus usingthe second identification information whereas the first user isprohibited from supplying power to his/her load apparatus. That is, thepower management system can appropriately transfer or moveidentification information from the first user to the second user.

The accumulated value of the amount of surplus power corresponding tothe first time period may include, for example, a value obtained byadding surplus power values corresponding to a period from a start ofthe first time period including a reception time, which is a time atwhich the inquiry has been received, to the reception time to anestimated accumulated value of the amount of surplus power from thereception time to an end of the first time period.

According to the above aspect, in the power management system, the sumof the surplus power actually caused in the time period and the surpluspower estimated to be caused in the time period can be supplied to theload apparatus. As a result, it is possible to avoid increasing a powerprocurement cost of a retailer.

A power management system according to an aspect of the presentdisclosure is a power management system including a power generationapparatus corresponding to first user identification information, afirst load apparatus used by a user corresponding to the first useridentification information, and a power supply apparatus capable ofsupplying power to the first load apparatus and installed in a placedifferent from the power generation apparatus. The power managementsystem including one or more memories; and circuitry operative to:receive; from a meter that measures amount of surplus power, which is,in power generated by the power generation apparatus, power suppliedfrom the power generation apparatus to a power system, a surplus powervalue indicating the amount of surplus power, receive, from a firstcommunication terminal used by the user corresponding to the first useridentification information, an inquiry about power supply in which thesurplus power is used in a first time period that lasts a certain unittime, the inquiry being associated with the first user identificationinformation, issue, in accordance with the inquiry, first poweridentification information for validating power supply performed by thepower supply apparatus using the surplus power corresponding to thefirst time period for an accumulated value of the amount of surpluspower corresponding to the first time period, transmit the first poweridentification information and the accumulated value of the amount ofsurplus power corresponding to the first time period to the firstcommunication terminal, and cause the power supply apparatus that hasreceived, from the first communication terminal, a first power supplyrequest, which is associated with the first power identificationinformation, indicating that power is to be supplied to the first loadapparatus to supply an amount of first power equal to or smaller thanthe amount of surplus power to the first load apparatus as power thatdoes not cause a charging process.

According to the above aspect, the same advantageous effects as thoseproduced by the power management method can be produced.

A power supply apparatus according to an aspect of the presentdisclosure is a power supply apparatus connected to the power managementsystem.

According to the above aspect, the same advantageous effects as thoseproduced by the power management method can be produced.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium such as a CD-ROM, or any selective combinationthereof.

Embodiments will be specifically described hereinafter with reference tothe drawings.

It should be noted that the following embodiments are general orspecific examples. Values, shapes, materials, components, positions atwhich the components are arranged, how the components are connected toone another, steps, the order of steps, and the like are examples, anddo not limit the present disclosure. Components in the followingdescription that are not described in the independent claims, whichdefine broadest concepts, are described as arbitrary components.

First Embodiment

In a first embodiment, a power management system will be describedcapable of making wider use of surplus power caused in a user's home byconsuming the surplus power at a place different from the user's home.

First, a situation in which the power management system according to thepresent embodiment manages power will be described using an example.Power management performed by the power management system according tothe present embodiment, however, is not limited to this example.

The user drives an EV to go to a supermarket and charges the EV duringshopping. A power supply apparatus for charging EVs is installed in aparking lot of the supermarket, and the user charges the EV using thepower supply apparatus. A power generation apparatus is installed in theuser's home and generating power. While the user is charging the EV,surplus power is caused in the user's home because the amount of powerconsumed by a load apparatus in the user's home is smaller than theamount of power generated. The power management system performsmanagement such that the surplus power caused in the user's home offsetsthe power supplied to the EV from the power supply apparatus. The powermanagement system that performs such power management will bespecifically described hereinafter.

FIG. 1 is an overview of the configuration of a power management system1 according to the present embodiment. FIG. 2 is a block diagramillustrating the configuration of the power management system 1according to the present embodiment. In FIG. 1 and other drawings, solidlines indicate transmission of power, and broken lines indicatetransmission of information or control. The power management system 1will be described with reference to these drawings.

As illustrated in FIGS. 1 and 2, the power management system 1 accordingto the present embodiment includes a power supply apparatus 10, a home20 of a user U1, a retailer 40, and a transmission and distributionnetwork 50.

The power supply apparatus 10 is connected to the transmission anddistribution network 50 and supplies power supplied from thetransmission and distribution network 50 to a load apparatus 32. Thepower supply apparatus 10 holds a power ID of surplus power and suppliesan amount of power (also referred to as “first power”) equal to orsmaller than the amount of the surplus power associated with the heldpower ID to the load apparatus 32 from the transmission and distributionnetwork 50.

The power supply apparatus 10 includes an input interface 11 and a powersupply unit 12.

The input interface 11 is a user interface that receives an operationperformed by the user U1 or information. The input interface 11 may be anear field communication port that communicates information with acommunication terminal 31 through near field communication or the like,or may be keys or buttons that receive an operation performed by theuser U1 when pressed.

The power supply unit 12 is a power output unit that supplies powersupplied from the transmission and distribution network 50 to the loadapparatus 32. The power supply unit 12 supplies power to the loadapparatus 32 connected to the power supply unit 12 on the basis ofcontrol performed by a power management apparatus 41. More specifically,the power supply unit 12 supplies an amount of power specified by thepower management apparatus 41 to the load apparatus 32.

Even if the power management apparatus 41 does not specify an amount ofpower, the power supply unit 12 supplies an amount of power (alsoreferred to as “second power”) separately specified by the user U1 oranother person to the load apparatus 32. A charging process performed bythe power management apparatus 41 after the power supply unit 12supplies the second power, however, is different from a charging processperformed after the first power is supplied.

A control unit 13 is a processing unit that controls the operation ofthe power supply apparatus 10 on the basis of information obtained fromthe input interface 11 or the like. The control unit 13 supplies powerto the load apparatus 32 in accordance with a power supply requestreceived from the communication terminal 31 through the input interface11. More specifically, if a power ID included in a power supply requestis input, the control unit 13 inquires about the power ID included inthe power supply request and supplies an amount of power smaller thanthe amount of surplus power associated with the power ID to the loadapparatus 32 from the power supply unit 12.

The power ID used is not limited to one included in a power supplyrequest. The power ID used may be one obtained by another method, or maybe one generated by the control unit 13 itself, instead. That is, thecontrol unit 13 may inquire about a power ID held thereby and supply anamount of power smaller than the amount of surplus power associated withthe power ID to the load apparatus 32 from the power supply unit 12.

A power generation apparatus 21, a load apparatus 22, and a meter 23 areinstalled in the home 20 of the user U1.

The power generation apparatus 21 generates power and outputs thegenerated power to the outside. The power generation apparatus 21supplies surplus power, which is power generated thereby except forpower consumed by the load apparatus 22, that is, power obtained bysubtracting the power consumed by the load apparatus 22 from the powergenerated thereby, to the transmission and distribution network 50(reverse flow). The power generation apparatus 21 is realized, forexample, by a solar panel or a fuel cell. The power generation apparatus21 includes a device (e.g., a power conditioner) that converts powerobtained from a solar panel, a fuel cell, or the like into power thatcan be supplied to the load apparatus 22 or the like. The powergeneration apparatus 21 corresponds to a power generation apparatuscorresponding to first user identification information.

The load apparatus 22 is an apparatus that consumes power, that is, forexample, a home appliance or an EV. The load apparatus 22 may be astorage battery, instead. The load apparatus 22 corresponds to a secondload apparatus.

As illustrated in FIG. 2, the meter 23 is mounted on a power line andmeasures the amount of power that flows therethrough. The meter 23measures the amount of surplus power (the so-called amount of powersold) supplied to the transmission and distribution network 50 from thehome 20 of the user U1 in each measurement period and transmits theamount of power measured to the power management apparatus 41. Themeasurement period herein refers to a period of a predetermined lengthin which the meter 23 keeps measuring the amount of power. Although anexample in which the length of the measurement period is 5 minutes willbe described hereinafter, the length of the measurement period is notlimited to this. The length of the measurement period may be arbitrarilydetermined insofar as the length is shorter than the length of a timeperiod (described later). The length of the measurement may be, forexample, 1 minute or 10 minutes. If the power management apparatus 41inquires of the meter 23 about the amount of power in a certain periodin the past or present, the meter 23 transmits a value indicating theamount of power in the certain period in response to the inquiry.

The user U1 stays near the power supply apparatus 10 installed in aplace different from the home 20. The user U1 owns the communicationterminal 31 and the load apparatus 32.

The communication terminal 31 communicates with the power supplyapparatus 10 and the power management apparatus 41 on the basis ofoperations performed by the user U1. More specifically, thecommunication terminal 31 communicates with the power managementapparatus 41 to inquire about the possibility of power supply and obtaina power ID necessary to supply power from the power supply apparatus 10.The communication terminal 31 communicates with the power supplyapparatus 10 to transmit the power ID to the power supply apparatus 10and supply power to the load apparatus 32 from the power supplyapparatus 10. The communication terminal 31 is, for example, asmartphone, a mobile phone terminal, a personal computer (PC), or thelike.

The load apparatus 32 is an electric device owned or carried by the userU1. The load apparatus 32 receives power from the power supply apparatus10 if the communication terminal 31 transmits a power ID to the powersupply apparatus 10. The load apparatus 32 is, for example, a mobileterminal, an EV, or the like. The load apparatus 32 may be thecommunication terminal 31, instead. The load apparatus 32 may be anyelectric device used by the user U1, and it does not matter whether theuser U1 has the ownership of the electric device. The load apparatus 32corresponds to a first load apparatus.

The retailer 40 is a power retailer that makes money by supplying powerto consumers. The retailer 40 makes a power supply contract with theuser U1 using the power management apparatus 41 and charges the user U1a price corresponding to the amount of power used by the load apparatus22 in the home 20 of the user U1 and the amount of power used by theload apparatus 32 through the power supply apparatus 10.

The power management apparatus 41 obtains the amount of surplus powersupplied in a certain period from the meter 23 of the home 20 of theuser U1 in accordance with an inquiry from the communication terminal 31about the possibility of power supply in order to identify surplus powercaused in the certain period. The power management apparatus 41 thengenerates a power ID for uniquely identifying the identified surpluspower and transmits the generated power ID to the communication terminal31. The power management apparatus 41 may periodically obtain the amountof surplus power from the meter 23 of the home 20 of the user U1,instead.

The power ID is not only a value indicating the amount of power but alsoinformation associated with power identified by a place from which thepower is supplied, a period in which the power is supplied, the amountof power, and the like. More specifically, the power ID generated asabove may be information associated with the amount of power suppliedfrom the home 20 of the user U1 in the certain period, the informationbeing identified by the meter 23. The power ID corresponds to firstidentification information. A method for identifying surplus power willbe described in detail later.

The power management apparatus 41 performs a process for charging theuser U1 the price of power consumed by the user U1. More specifically,the power management apparatus 41 performs a process for charging theuser U1 the price of power consumed in the home 20 of the user U1. As arule, if the power supply apparatus 10 has supplied power to the loadapparatus 32 of the user U1, the power management apparatus 41 performsa process for charging the user U1 the price of the supplied power. Asan exception, however, if the power supply apparatus 10 has suppliedpower (first power) after holding a power ID, the power managementapparatus 41 does not perform a process for charging the user U1 theprice of the supplied power, that is, prohibits the charging process. Inthe power supplied to the load apparatus 32 from the power supplyapparatus 10, the first power is power that does not cause a chargingprocess. Power other than the first power is the second power. That is,if the power supply apparatus 10 has supplied power (second power) tothe load apparatus 32 of the user U1 without holding a power ID, thepower management apparatus 41 performs a process for charging the userU1 the price of the supplied power. The second power is power thatcauses a charging process.

The power management apparatus 41 (more specifically, a settlementprocess unit 427, which will be described later) performs a process forpaying the user U1 money corresponding to the amount of surplus powersupplied from the home 20 of the user U1. If the first power has beensupplied to the load apparatus 32, the power management apparatus 41performs a process for paying the user U1 money corresponding to theamount of power obtained by subtracting the amount of the first powerfrom the amount of surplus power.

The transmission and distribution network 50 is connected to a powersystem of a power company or a part of the power system. Thetransmission and distribution network 50 is a network that distributesgrid power. The transmission and distribution network 50 supplies powerto the home 20 of the user U1 and the power supply apparatus 10.

The power supply apparatus 10 may further include a reception unit (notillustrated) that receives money corresponding to the amount of powersupplied. If the power supply apparatus 10 has supplied power to theload apparatus 32 of the user U1 and the power management apparatus 41does not perform a charging process, the reception unit receives, fromthe user U1, money corresponding to the amount of power supplied. As anexception, however, if the power supply apparatus 10 has supplied thefirst power, the reception unit does not receive, from the user U1,money corresponding to the amount of power supplied, that is, prohibitsthe reception of the money.

The reception unit is a slot into which bills and coins can be thrown, acombination of a card slot that reads information from a card having asettlement function and a communication unit, or a communication unitthat reads information from the communication terminal 31 having asettlement function. The reception unit, however, is not limited tothese examples.

In the power management system 1, power supply-demand balance isadjusted in each time period, which is a unit time in which thesupply-demand balance is adjusted. The power supply apparatus 10 maysupply the first power in the same time period in which the powergeneration apparatus 21 supplies surplus power to the transmission anddistribution network 50. In doing so, the power management system 1 cansupply power to the load apparatus 32 without disrupting the powersupply-demand balance in the time period. As a result, it is possible toavoid increasing a power procurement cost.

FIG. 3 is a schematic diagram specifically illustrating a part of thepower management system 1 according to the present embodiment includingthe home 20 of the user U1.

As illustrated in FIG. 3, the home 20 of the user U1 is connected to thetransmission and distribution network 50, and other houses 20A and 20Bare also connected to the transmission and distribution network 50. Thehouses 20A and 20B may be houses having the same functions as the home20 of the user U1, or may be conventional houses that do not includepower generation equipment or the like.

As described above, the power generation apparatus 21, the loadapparatus 22, and the meter 23 are installed in the home 20 of the userU1. An electric switchboard 24 and a meter 25 may also be installed inthe home 20 of the user U1.

The electric switchboard 24 is connected to the transmission anddistribution network 50, the power generation apparatus 21, and the loadapparatus 22. If the amount of power generated by the power generationapparatus 21 exceeds the amount of power consumed by the load apparatus22, the electric switchboard 24 supplies power to the transmission anddistribution network 50. If the amount of power generated by the powergeneration apparatus 21 falls below the amount of power consumed by theload apparatus 22, the electric switchboard 24 receives power from thetransmission and distribution network 50.

The meter 25 is a measuring device that is mounted on a power line andthat measures the amount of power that flows therethrough. The meter 25measures the amount of power (the so-called amount of power purchased)flowing from the transmission and distribution network 50 to the home 20of the user U1 in each measurement period and transmits a valueindicating the measured amount of power to the power managementapparatus 41.

Next, the power management apparatus 41 will be described in detail.

FIG. 4 is a block diagram illustrating specific function blocks of thepower management apparatus 41 according to the present embodiment.

As illustrated in FIG. 4, the power management apparatus 41 includes apower information obtaining unit 421, a surplus power identificationunit 422, a communication unit 423, a power ID management unit 424, apower supply possibility determination unit 425, a surplus power usehistory management unit 426, and the settlement process unit 427.

The power information obtaining unit 421 is a processing unit thatobtains the amount of power sold in each time period, that is, theamount of surplus power, from the meter 23. The power informationobtaining unit 421 can also obtain the amount of power purchased in eachtime period from the meter 25. The power information obtaining unit 421then associates the amount of power sold and the amount of powerpurchased with the power supply contract and stores the amount of powersold, the amount of power purchased, and the power supply contract in apower information management table. The power information obtaining unit421 also associates the amount of surplus power with the power supplycontract and stores the amount of surplus power and the power supplycontract in a surplus power information table.

The surplus power identification unit 422 is a processing unit thatreceives an inquiry about the possibility of power supply from thecommunication terminal 31 and that identifies surplus power in a timeperiod on the basis of the amount of surplus power in each measurementperiod obtained by the power information obtaining unit 421.

More specifically, the surplus power identification unit 422 receives aninquiry about the possibility of power supply from the communicationterminal 31 through the communication unit 423. Upon receiving theinquiry about the possibility of power supply, the surplus poweridentification unit 422 identifies an accumulated value of the amount ofsurplus power in each measurement period obtained by the powerinformation obtaining unit 421 as the amount of surplus power in thetime period. Alternatively, the surplus power identification unit 422may identify the amount of surplus power in the time period by adding anestimated value of the amount of surplus power that has not beenobtained to the accumulated value of the amount of surplus power in eachmeasurement period obtained by the power information obtaining unit 421.

The communication unit 423 is a communication interface for enabling thefunction blocks of the power management apparatus 41 to communicate withthe communication terminal 31.

The power ID management unit 424 is a processing unit that issues apower ID and that associates the power ID with an accumulated value ofthe amount of surplus power identified by the surplus poweridentification unit 422. The power ID management unit 424 transmits theidentified amount of surplus power to the communication terminal 31through the communication unit 423. The power ID management unit 424associates the amount of surplus power and the power ID with each otherand stores the amount of surplus power and the power ID in a power IDmanagement table. Each power ID may be provided with an expiration time.As the expiration time, an end time of a time period including a time atwhich each power ID has been issued is used. The power ID managementunit 424 can then manage power IDs whose expiration times have not yetcome as valid power IDs and power IDs whose expiration times have comeas invalid power IDs. If a power ID indicated in a record is valid, thepower ID can be used, that is, more specifically, the power supplyapparatus 10 can supply power using the power ID. If a power IDindicated in a record is invalid, the power ID is not valid. In thiscase, the power ID cannot be used, that is, the power supply apparatus10 cannot supply power using the power ID.

The power supply possibility determination unit 425 is a processing unitthat determines whether the amount of power indicated in a power supplyrequest received from the power supply apparatus 10 can be supplied.

The surplus power use history management unit 426 is a processing unitthat receives a power supply report after the power supply apparatus 10supplies power and that updates surplus power use information. Thesurplus power use history management unit 426 associates a power ID andthe amount of power supplied using the power ID with each other andstores the power ID and the amount of power in a surplus power useinformation table. The surplus power use history management unit 426associates a contract ID and the amount of power supplied from the powersupply apparatus 10 using the contract ID with each other and stores thecontract ID and the amount of power in a power supply apparatus useinformation table.

The settlement process unit 427 is a processing unit that performs aprocess for settling an electricity bill on the basis of the amount ofpower purchased and the amount of power sold in the home 20 of the userU1. The settlement process unit 427 performs the process for settling anelectricity bill in consideration of power supplied from the powersupply apparatus 10.

FIG. 5 is a diagram illustrating a surplus power information table T10according to the present embodiment.

The surplus power information table T10 is a table held by the powerinformation obtaining unit 421. In the surplus power information tableT10, the amount of surplus power in each measurement period obtained bythe power information obtaining unit 421 from the meter 23 is stored asa record. Items of the surplus power information table T10 will bedescribed hereinafter.

“Contract ID” is an ID for uniquely identifying a power supply contractin which the amount of surplus power indicated in a corresponding recordhas been caused.

“Meter ID” is an ID for uniquely identifying the meter 23 that hasmeasured the amount of surplus power indicated in the correspondingrecord.

“Measurement period start time” is a start time of a measurement periodin which the amount of surplus power indicated in the correspondingrecord has been caused.

“Measurement period end time” is an end time of the measurement periodin which the amount of surplus power indicated in the correspondingrecord has been caused.

“Amount of surplus power” is the amount of surplus power indicated inthe corresponding record and expressed, for example, in Wh.

A first record in the surplus power information table T10 illustrated inFIG. 5, for example, indicates that, in a power supply contract whosecontract ID is “00001”, a meter 23 whose meter ID is “123456789” hasmeasured a surplus power of 340 Wh in a measurement period “04/01/201510:30:00 to 10:35:00”.

FIG. 6 is a diagram illustrating a power ID management table T20according to the present embodiment.

The power ID management table T20 is a table held by the power IDmanagement unit 424. In the power ID management table T20, a power IDissued by the power ID management unit 424 and associated with theamount of surplus power is stored as a record. Items of the power IDmanagement table T20 will be described hereinafter.

“Power ID” is a power ID indicated in a corresponding record.

“Expiration time” is an expiration time of the power ID indicated in thecorresponding record, that is, at time at which the power ID expires.

“Amount of surplus power” is the amount of surplus power associated withthe power ID indicated in the corresponding record, that is, the amountof surplus power associated when the power ID has been issued.

“Amount of power available” is the amount of power available in theamount of surplus power associated with the power ID indicated in thecorresponding record. The amount of power available is the same as theamount of surplus power immediately after the power ID issued, butdecreases as the surplus power is consumed.

“Record registration time” is a time at which the corresponding recordhas been registered.

A first record in the power ID management table T20 illustrated in FIG.6, for example, indicates that a power ID “1504011040766” is associatedwith a surplus power of 766 Wh and a power of 766 Wh is available. Theexpiration time of the power ID is “04/01/2015 11:00:00”, and the timeat which the record has been registered is “04/01/2015 10:40:00”.

FIG. 7 is a diagram illustrating a surplus power use information tableT30 according to the present embodiment.

The surplus power use information table T30 is a table held by thesurplus power use history management unit 426. In the surplus power useinformation table T30, the amount of power used by the power supplyapparatus 10 for supplying power is stored as a record.

“Power ID” is a power ID associated with the amount of powerused forpower supply indicated in a corresponding record.

“Power supply start time” is a time at which the power supply apparatus10 indicated in the corresponding record has started supplying power.

“Power supply end time” is a time at which the power supply apparatus 10indicated in the corresponding record has stopped supplying power.

“Amount of power supplied” is the amount of power supplied by the powersupply apparatus 10 indicated in the corresponding record.

“Power supply apparatus ID” is an ID for uniquely identifying the powersupply apparatus 10 indicated in the corresponding record that hassupplied power.

“Record registration time” is a time at which the corresponding recordhas been registered.

A record in the surplus power use information table T30 illustrated inFIG. 7 indicates that a power of 500 Wh associated with the power ID of“1504011040766” has been supplied by a power supply apparatus 10 whosepower supply apparatus ID is “abcde98765” in “04/01/2015 10:45:00 to10:50:00”. The record has been registered at “04/01/2015 10:50:00”.

FIG. 8 is a diagram illustrating a power information management tableT40 according to the present embodiment.

The power information management table T40 is a table held by the powerinformation obtaining unit 421. In the power information managementtable T40, the amount of power purchased and the amount of power sold inthe home 20 of the user U1 in each time period are stored as a record.

“Contract ID” is an ID for uniquely identifying a power supply contractin which the amount of power purchased and the amount of power soldindicated in a corresponding record have been measured.

“Meter ID” is an ID for uniquely identifying the meters (the meter 23and the meter 25) that have measured the amount of power purchased andthe amount of power sold indicated in the corresponding record.

“Time period start time” is a start time of a time period in which theamount of power purchased and the amount of power sold indicated in thecorresponding record have been measured.

“Time period end time” is an end time of a time period in which theamount of power purchased and the amount of power sold indicated in thecorresponding record have been measured.

“Amount of power purchased” is a value indicating the amount of powerpurchased indicated in the corresponding record and expressed, forexample, in Wh.

“Amount of power sold” is a value indicating the amount of power soldindicated in the corresponding record and expressed, for example, in Wh.

A first record in the power information management table T40 illustratedin FIG. 8, for example, indicates that, in the power supply contractwhose contract ID is “00001”, the meter 23 whose meter ID is “123456789”has measured a purchased power of 0 Wh and a sold power of 1,000 Wh in atime period “04/01/2015 10:00:00 to 10:30:00”.

FIG. 9 is a diagram illustrating a power supply apparatus useinformation table T50 according to the present embodiment.

The power supply apparatus use information table T50 is a table held bythe surplus power use history management unit 426. In the power supplyapparatus use information table T50, the amount of surplus power and theamount of grid power in the amount of power supplied by the power supplyapparatus 10 are stored as a record.

“Contract ID” is an ID for uniquely identifying a power supply contractrelating to the amount of surplus power supplied and the amount of gridpower supplied indicated in a corresponding record.

“Power supply apparatus ID” is an ID for uniquely identifying the powersupply apparatus 10 that has performed power supply relating to thecorresponding record.

“Power supply period start time” is a start time of a period in whichthe power supply relating to the corresponding record has beenperformed.

“Power supply period end time” is an end time of the period in which thepower supply relating to the corresponding record has been performed.

“Amount of power supplied” is a value indicating the amount of powersupplied relating to the record and expressed, for example, in Wh.

“Amount of surplus power supplied” is a value indicating the amount ofsurplus power in the amount of power supplied relating to thecorresponding record and expressed, in Wh.

“Amount of grid power supplied” is a value indicating the amount of gridpower in the amount of power supplied relating to the correspondingrecord and expressed, in Wh.

A first record in the power supply apparatus use information table T50illustrated in FIG. 9, for example, indicates that, in the power supplycontract whose contract ID is “00001”, the power supply apparatus 10whose power supply apparatus ID is “abcde98765” supplies a power of 500Wh. In this power, the amount of surplus power supplied is 500 Wh, andthe amount of grid power supplied is 0 Wh.

Next, the method for identifying surplus power, a method for inquiringabout the possibility of power supply, and a method for responding to aninquiry will be described.

FIG. 10 is a diagram illustrating surplus power according to the presentembodiment. FIG. 10 is a diagram illustrating the method for identifyingsurplus power used by the power management apparatus 41.

FIG. 10 illustrates changes in the amount of surplus power, which is theamount of power generated by the power generation apparatus 21 andsupplied to the transmission and distribution network 50, over time. A“time period” illustrated in FIG. 10 refers to a unit time in which theretailer 40 needs to achieve balancing between supply and demand ofpower. That is, the retailer 40 controls power supply-demand balancesuch that supply and demand match in the time period. A time period xillustrated in FIG. 10 is a period from a time T(x) to a time T(x+1).

The power management apparatus 41 obtains the amount of surplus power301 illustrated in FIG. 10 by obtaining the amount of power measured bythe meter 23, that is, the amount of power flowing from the home 20 ofthe user U1 to the transmission and distribution network 50. FIG. 10illustrates a case in which, when the power management apparatus 41obtains the amount of power from the meter 23, the meter 23 has obtainedand held the amount of power before a time T(x)+t.

The power management apparatus 41 sums the amount of surplus power 301obtained from the meter 23 to identify the amount of surplus power EP1in the time period x.

The power management apparatus 41 may identify the expected amount ofsurplus power 302 in a part of the time period x after the time T(x)+tas well as the amount of surplus power 301 obtained from the meter 23.In this case, the power management apparatus 41 may identify the amountof surplus power EP2 in the time period x by summing the amount ofsurplus power 301 and the amount of surplus power 302. In doing so, theamount of surplus power caused in the time period x can be used moreefficiently in the power management system 1.

FIG. 11 is a diagram illustrating an inquiry about the possibility ofpower supply and a response to the inquiry according to the presentembodiment. FIG. 11 illustrates the amount of surplus power identifiedby the surplus power identification unit 422 after an inquiry about thepossibility of power supply is made in a time period y.

If the communication terminal 31 inquires of the power managementapparatus 41 about the possibility of power supply at 10:17, the surpluspower identification unit 422 identifies the amount of surplus power as800 Wh by accumulating the amount of power (340 Wh, 426 Wh, and 34 Wh)in measurement periods from 10:30 to 10:45 that have already beenobtained by the power information obtaining unit 421. The surplus poweridentification unit 422 then transmits a value indicating the amount ofsurplus power to the communication terminal 31 as a response.

When identifying surplus power, the surplus power identification unit422 may estimate the amount of surplus power in measurement periods inthe time period y from which the amount of surplus power has not yetbeen obtained and add an accumulated value of the estimated amount ofsurplus power to the aforementioned amount of surplus power. Morespecifically, the surplus power identification unit 422 may identify theamount of surplus power in the time period y as 1,600 Wh, for example,by estimating that the amount of surplus power in measurement periodsfrom 10:45 to 11:00 is the same as that in the time periods from 10:30to 10:45.

Next, a process performed by the power management system 1 will bedescribed.

FIG. 12 is a flowchart illustrating an overall process performed by thepower management system 1 according to the present embodiment.

The power management system 1 performs processing in steps S11 to S14for each time period (loop A).

In steps S11 to S14, the power management system 1 performs the processfor inquiring about the possibility of power supply, the process foridentifying surplus power, the process for requesting power supply, andthe process for reporting power supply.

The power management system 1 also performs a settlement process in acycle independent of the above processes performed in each time period(step S15). The cycle may have any length insofar as the cycle is longerthan each time period. The length of the cycle may be, for example, amonth.

Details of processing in the above steps will be described hereinafter.

FIG. 13 is a sequence diagram illustrating transmission of informationin the power management system 1 according to the present embodimentfrom the inquiry about the possibility of power supply to the powersupply report. The process performed by the power management system 1will be described in more detail with reference to FIG. 13.

Steps illustrated in FIG. 13 are included in the processing stepsillustrated in FIG. 12. Step S101 illustrated in FIG. 13, for example,is processing included in step S11 illustrated in FIG. 12, and stepsS102 to S105 illustrated in FIG. 13 are processing included in step S12illustrated in FIG. 12. Steps S111 to S114 illustrated in FIG. 13 areprocessing included in step S13 illustrated in FIG. 12, and step S115illustrated in FIG. 13 is processing included in step S14 illustrated inFIG. 12. This, however, is an example, and relationships between stepsare not limited to this.

In step S101, the communication terminal 31 of the user U1 transmits aninquiry about the possibility of power supply to the power managementapparatus 41. The power management apparatus 41 receives the inquiryabout the possibility of power supply. The inquiry about the possibilityof power supply is used for inquiring of the power management apparatus41 whether the power supply apparatus 10 in the power management system1 can supply power, that is, whether the home 20 of the user U1 causessurplus power. When inquiring about the possibility of power supply, thecommunication terminal 31 transmits a contract ID, which is an ID foruniquely identifying a contract between the user U1 and the retailer 40.Alternatively, the communication terminal 31 may transmit a user ID,which is an ID for uniquely identifying the user U1, instead of thecontract ID, while associating the user ID with the inquiry about thepossibility of power supply. The user ID of the user U1 will also bereferred to as “first user identification information”.

The communication terminal 31 transmits the inquiry about thepossibility of power supply to the power management apparatus 41 using acommunication path through a communication line. Alternatively, theinquiry about the possibility of power supply may be automaticallytransmitted, for example, after a certain application is activated on asmartphone, which is the communication terminal 31, or after the user U1performs a certain operation.

In step S102, the power management apparatus 41 transmits an inquiryabout the amount of surplus power to the meter 23 of the home 20 of theuser U1. The power management apparatus 41 requests the meter 23 tooutput a value indicating the amount of surplus power corresponding to atime period including a reception time, which is a time at which theinquiry about the possibility of power supply in step S101 has beenreceived (input). More specifically, the power management apparatus 41identifies the user U1 by referring to the contract ID included in theinquiry about the possibility of power supply in step S101. The powermanagement apparatus 41 then transmits the inquiry about the amount ofsurplus power to request the meter 23 of the home 20 of the identifieduser U1 to transmit the value indicating the amount of surplus powermeasured by the meter 23 thereto. Alternatively, the power managementapparatus 41 may include information for identifying a period of theamount of surplus power to be obtained in the inquiry about the amountof surplus power and transmit the inquiry.

In step S103, the meter 23 transmits the value indicating the amount ofsurplus power to the power management apparatus 41 in accordance withthe inquiry about the amount of surplus power received from the powermanagement apparatus 41 in step 3102. The power management apparatus 41receives the amount of surplus power transmitted from the meter 23. Themeter 23 may transmit individual values (340 Wh, 426 Wh, and 34 Wh inthe example illustrated in FIG. 11) indicating the amount of surpluspower in measurement periods in the time period including a current timeor may transmit an accumulated value (800 Wh in the example illustratedin FIG. 11) of the amount of surplus power in the measurement periods inthe time period including the current time. In the followingdescription, the former will be taken as an example. If a period isspecified in step S102, the meter 23 transmits a value indicating theamount of surplus power in the period identified by the information tothe power management apparatus 41. The power management apparatus 41stores the received values indicating the amount of surplus power in thesurplus power information table T10.

In step S104, the power management apparatus 41 identifies surplus poweron the basis of the amount of surplus power obtained in step S103. Thepower management apparatus 41 issues a power ID, which is an ID foruniquely identifying the surplus power, and gives the power ID to theidentified surplus power. In other words, the power management apparatus41 identifies the surplus power on the basis of the amount of surpluspower obtained in step S103 and issues the power ID, which is the ID foruniquely identifying the surplus power, while associating the power IDwith the surplus power. More specifically, the power managementapparatus 41 identifies the surplus power by calculating an accumulatedvalue of the amount of surplus power in the measurement periods obtainedin step S103. The identification of the surplus power and the provisionof the power ID in this step are performed in accordance with theinquiry about the possibility of power supply in step S101. The power IDis information for validating power supply performed by the power supplyapparatus 10 using the surplus power corresponding to the time periodincluding the current time.

In step S105, the power management apparatus 41 transmits, to thecommunication terminal 31, the power ID given in step S104. Whentransmitting the power ID, the power management apparatus 41 notifiesthe communication terminal 31 of the amount of power available. Theamount of power available is the same as the amount of surplus poweridentified in step S104 and indicates the amount of power that can besupplied from the power supply apparatus 10 using the power ID. Insteadof transmitting the power ID to the communication terminal 31, the powermanagement apparatus 41 may let the user U1 obtain the power ID in amanner that a person can understand the power ID. The user U1 may, forexample, obtain a paper medium on which the power ID is written, or theuser U1 may hear the power ID as a speech sound.

In step 3105, the power management apparatus 41 may determine whether ornot the accumulated value of the amount of surplus power correspondingto the time period is equal to or smaller than a certain minimum value.If the accumulated value of the amount of surplus power corresponding tothe time period is equal to or smaller than the certain minimum value,the power management apparatus 41 may perform control such that thepower ID is not issued or associated with the accumulated value of theamount of surplus power corresponding to the time period. In this case,the power management apparatus 41 may perform control such that thepower ID and the accumulated value are not transmitted to thecommunication terminal 31 in accordance with the inquiry of thepossibility of power supply. In addition, in this case, the powermanagement apparatus 41 may perform control in such a way as to notifythe communication terminal 31 that the accumulated value of the amountof surplus power corresponding to the time period is equal to or smallerthan the certain minimum value in accordance with the inquiry of thepossibility of power supply. In doing so, if the amount of power thatcan be supplied from the power supply apparatus 10 is equal to orsmaller than the certain minimum value, the power management apparatus41 can prohibit the power supply apparatus 10 from supplying power ornotify the user U1 of the prohibition.

In step S111, the communication terminal 31 sends a power supply requestto the power supply apparatus 10. The power supply request isinformation indicating that the user U1 desires to receive power withthe load apparatus 32. The power supply request includes the power IDtransmitted from the power management apparatus 41 in step S105 and theamount of power to be used, which is the amount of power that the userU1 desires to receive. The power supply apparatus 10 receives the powersupply request and the power ID included in the power supply request.Although the communication terminal 31 inputs the power supply requestto the power supply apparatus 10 in the above description, anotherapparatus may input the power supply request to the power supplyapparatus 10, instead. The amount of power to be used may be a valueequal to or smaller than the amount of power available associated withthe power ID, or may be a sign indicating the amount of power available.

The power supply request is transmitted, for example, by bringing thecommunication terminal 31 close to the near field communication portthat is the input interface 11 of the power supply apparatus 10 andperforming near field communication. Alternatively, the power supplyrequest may be transmitted through a communication line. Alternatively,the user U1 may manually input the power ID using the keys that are theinput interface 11 in order to transmit the power supply request.

In step S112, the power supply apparatus 10 inquires of the powermanagement apparatus 41 about the power ID obtained as a result of thepower supply request transmitted in step S111. More specifically, thepower supply apparatus 10 inquires of the power management apparatus 41whether the power ID is a legitimate, valid power ID that has beenissued by the power management apparatus 41. If the power ID has beenforged or is a copy of a power ID that has already been used in thepast, for example, it can be determined that the power ID is notlegitimate or, if the power ID corresponds to the amount of surpluspower in a past time period, not valid.

In the inquiry in step S112, the power supply apparatus 10 may alsoinquires of the power management apparatus 41 about the amount of powerto be used transmitted from the communication terminal 31 in step 6105.If the amount of power to be used exceeds the amount of power availablecorresponding to the power ID, it can be determined that the amount ofpower to be used is not reasonable.

In step S113, the power management apparatus 41 transmits, to the powersupply apparatus 10, a result of the inquiry about the power IDtransmitted in step S112. More specifically, if the power ID transmittedin step S112 is legitimate, the power management apparatus 41 transmitsa response indicating that the power ID is legitimate.

In step 6114, the power supply apparatus 10 supplies the amount of powerto be used received along with the power ID in the power supply requestto the load apparatus 32 connected thereto. At this time, the powersupply apparatus 10 does not receive money corresponding to the amountof power supplied, that is, prohibits the reception of money. In otherwords, the power supply apparatus 10 supplies power that does not causea charging process to the load apparatus 32. If, as described above, thepower supply apparatus 10 has supplied power to the load apparatus 32 onthe basis of a single power ID, the power supply apparatus 10 may beprevented from supplying power to the load apparatus 32 again on thebasis of the power ID. If the amount of power to be used is smaller thanthe amount of power available, the power supply apparatus 10 may supplypower again in the same time period on the basis of the power ID insofaras the sum of the amount of power supplied using the power ID is equalto or smaller than the amount of power available.

In step S115, if the power supply apparatus 10 has supplied power to theload apparatus 32 in step S114, the power supply apparatus 10 transmitsa power supply report to the power management apparatus 41. The powersupply report includes the power ID and the amount of power supplied.

Although the meter 23 transmits a value indicating the amount of surpluspower in accordance with the inquiry about the amount of surplus powerin the above description, the meter 23 may periodically transmit a valueindicating the amount of surplus power, instead. That is, the processingin steps S101 to S105 illustrated in FIG. 13 may be replaced byprocessing illustrated in FIG. 14.

FIG. 14 is a sequence diagram illustrating transmission of informationin the power management system 1 according to a modification of thepresent embodiment from the process for inquiring about the possibilityof power supply to the process for reporting power supply.

In step S103A, the meter 23 periodically transmits a value indicatingthe amount of surplus power to the power management apparatus 41 in eachmeasurement period. The power management apparatus 41 periodicallyreceives the value indicating the amount of surplus power. The powermanagement apparatus 41 stores the received value indicating the amountof surplus power in the surplus power information table T10. Step S103Ais different from step 3103 in that the meter 23 automatically transmitsthe value indicating the amount of surplus power in step S103A.

In step S101A, the communication terminal 31 of the user U1 transmits aninquiry about the possibility of power supply to the power managementapparatus 41.

In step S104A, the power management apparatus 41 identifies surpluspower on the basis of the amount of surplus power obtained in step3103A. The power management apparatus 41 then issues a power ID, whichis an ID for uniquely identifying the surplus power, and gives the powerID to the identified amount of surplus power. More specifically, if thepower management apparatus 41 receives the inquiry about the possibilityof power supply in step 3101A, the power management apparatus 41accumulates values of the amount of surplus power corresponding to aperiod from a start time of a time period including a reception time,which is a time at which the inquiry about the possibility of powersupply has been received, to the reception time. The power managementapparatus 41 then generates an accumulated value of the amount ofsurplus power corresponding to the time period to identify the surpluspower.

Step S105 is the same as step S105 illustrated in FIG. 13.

FIG. 15 is a sequence diagram illustrating transmission of informationin the power management system 1 according to the present embodimentduring the charging process. The process performed by the powermanagement system 1 will be described in more details with reference toFIG. 15.

Steps illustrated in FIG. 15 are included in the processing stepsillustrated in FIG. 12. Steps S122 to S124 illustrated in FIG. 15, forexample, are included in step 315 illustrated in FIG. 12. This, however,is an example, and relationships between steps are not limited to this.

In step S122, the power management apparatus 41 performs the settlementprocess. In the settlement process, a price obtained by subtractingmoney (a price) corresponding to the amount of surplus power suppliedfrom the home 20 of the user U1 from a price corresponding to the amountof power supplied to the load apparatus 22 from the transmission anddistribution network 50 and consumed is calculated as a bill to be sentto the user U1 on the basis of the power supply contract between theretailer 40 and the user U1. At this time, the price is calculated whilesubtracting the amount of power supplied from the power supply apparatus10 in step S114 from the amount of surplus power supplied from the home20 of the user U1.

In step S123, the retailer 40 sends the bill (electricity bill)calculated in the settlement process in step S122 to the user U1.

In step 3124, the user U1 pays the electricity bill sent thereto in step3123.

Steps S112 and S113 need not necessarily be performed if it is clearthat the power supply apparatus 10 holds a legitimate power ID.

The charging process in step S122 and the sending of a bill in step 3123are performed in each period specified in the power supply contractbetween the retailer 40 and the user U1. The charging process isperformed, for example, each month.

Details of processes performed by the function blocks of the powermanagement apparatus 41 will be described hereinafter.

In step S11 illustrated in FIG. 12, the communication terminal 31 onlyinquires of the power management apparatus 41 about the possibility ofpower supply, and description of details of this processing is omitted.

FIG. 16 is a flowchart illustrating the process performed by the powermanagement apparatus 41 according to the present embodiment. Theflowchart of FIG. 16 illustrates the process performed by the powermanagement apparatus 41 in step S12 illustrated in FIG. 12.

In step S601, the surplus power identification unit 422 identifies theamount of surplus power. Step S601 corresponds to step S104 (FIG. 13) orstep 3104A (FIG. 14). The processing in step S601 will be described indetail later.

In step S602, the surplus power identification unit 422 determineswhether or not the amount of surplus power identified in step 3601 isequal to or larger than a certain value. If the surplus poweridentification unit 422 determines that the amount of surplus power isequal to or larger than the certain value, the process proceeds to stepS603. On the other hand, if the surplus power identification unit 422determines that the amount of surplus power is not equal to or largerthan the certain value (that is, smaller than the certain value), theprocess proceeds to step S605.

In step S603, the power ID management unit 424 gives a power ID tosurplus power corresponding to the amount of surplus power identified instep S601. Step S603 corresponds to step S104 (FIG. 13) or step S104A(FIG. 14).

In step 3604, the power ID management unit 424 transmits, to thecommunication terminal 31, the power ID given in step S603. The power IDmanagement unit 424 also transmits a value indicating the amount ofsurplus power identified in step S601 to the communication terminal 31as the amount of power available. The amount of power available is avalue indicating the amount of power available at a time when the powersupply apparatus 10 supplies the surplus power.

In step S605, the surplus power identification unit 422 notifies thecommunication terminal 31 that power cannot be supplied (power supply isimpossible).

As a result of the above process, the power management apparatus 41appropriately transmits the power ID in response to the inquiry aboutthe possibility of power supply from the communication terminal 31.

FIG. 17 is a first flowchart illustrating the process for identifyingsurplus power performed by the surplus power identification unit 422according to the present embodiment. This flowchart illustrates detailsof the processing in step S601 illustrated in FIG. 16 and is true in acase in which the meter 23 periodically transmits the value indicatingthe amount of surplus power to the power management apparatus 41 asillustrated in FIG. 14.

In step S701, the surplus power identification unit 422 obtains thecurrent time. A time period including the current time will be referredto as the “time period x”, and the start time of the time period x willbe denoted by T(x). In this case, the current time is expressed asT(x)+t. Here, t corresponds to time elapsed since T(x) until the currenttime.

In step S702, the start time T(x) of the time period including thecurrent time is identified on the basis of the current time T(x)+tobtained in step S701.

In step S703, the surplus power identification unit 422 calculates, inthe surplus power stored in the surplus power information table T10, thetotal amount of surplus power, that is, an accumulated value of theamount of surplus power, of a consumer corresponding to the contract IDfrom the time T(x) to a time up to which the amount of surplus power hasalready been obtained in the time period x.

As a result of the above process, the power management apparatus 41 canidentify the surplus power.

The process illustrated in FIG. 17 may be replaced by a processillustrated in FIG. 18.

FIG. 18 is a second flowchart illustrating the process for identifyingsurplus power performed by the power management apparatus 41 accordingto the present embodiment. This flowchart illustrates details of theprocessing in step S601 illustrated in FIG. 16 and is true in a case inwhich the meter 23 transmits the amount of surplus power to the meter 23in accordance with an inquiry about the amount of surplus power asillustrated in FIG. 13.

Steps S801 and S802 are the same as steps S701 and S702, respectively,illustrated in FIG. 17.

In step S803, the surplus power identification unit 422 requests themeter 23 of the consumer corresponding to the contract ID to transmitdata regarding the amount of surplus power after the start time T(x) ofthe time period including the current time. The surplus poweridentification unit 422 then obtains the data regarding the amount ofsurplus power in each measurement period after the time T(x).

In step S804, the surplus power identification unit 422 stores theobtained data regarding the amount of surplus power in the surplus powerinformation table T10. The surplus power identification unit 422 thencalculates, in the amount of surplus power stored in the surplus powerinformation table T10, the total amount of surplus power, that is, anaccumulated value of the amount of surplus power, of the consumercorresponding to the contract ID from the time T(x) to the current time.

FIG. 19 is a flowchart illustrating the process for inquiring about apower ID performed by the power management apparatus 41 according to thepresent embodiment. The flowchart of FIG. 19 illustrates the processingperformed by the power management apparatus 41 in step S13 illustratedin FIG. 12.

In step S901, the power supply possibility determination unit 425 of thepower management apparatus 41 receives an inquiry about a power ID fromthe power supply apparatus 10 through the communication unit 423. Thereceived inquiry about a power ID includes a power ID and the amount ofpower to be supplied from the power supply apparatus 10. The inquiryabout a power ID is transmitted from the power supply apparatus 10 (stepS112 illustrated in FIG. 13).

In step S902, the power supply possibility determination unit 425determines whether the power ID included in the inquiry about the powerID received in step S901 exists in the power ID management table T20. Ifthe power ID exists, the process proceeds to step S904. On the otherhand, if the power ID does not exist, the process proceeds to step S903.

In step S903, the power supply possibility determination unit 425transmits “invalid: illegitimate power ID” through the communicationunit 423 as an inquiry result (corresponds to step S113 illustrated inFIG. 13). The inquiry result “invalid: illegitimate power ID” indicatesthat because the power ID received in step S901 is illegitimate, thepower supply apparatus 10 cannot supply power using the power ID. Thepower supply apparatus 10 is therefore prohibited from supplying powerusing the power ID.

In step S904, the power supply possibility determination unit 425determines whether the expiration time of the power ID has come. If theexpiration time of the power ID has not come, the process proceeds tostep S906. On the other hand, if the expiration time of the power ID hascome (that is, the power ID has expired), the process proceeds to stepS905.

In step S905, the power supply possibility determination unit 425transmits “invalid: power ID has expired” through the communication unit423 as the inquiry result (corresponds to step S113 illustrated in FIG.13). The inquiry result “invalid: power ID has expired” indicates thatbecause the power ID received in step S901 has expired, the power supplyapparatus 10 cannot supply power using the power ID. The power supplyapparatus 10 is therefore prohibited from supplying power using thepower ID.

In step S906, the power supply possibility determination unit 425determines whether or not the amount of power included in the inquiryabout the power ID received in step S901 is equal to or smaller than theamount of power available corresponding to the power ID included in theinquiry about a power ID. The amount of power available corresponding tothe power ID is managed in the power ID management table T20. If theamount of power is equal to or smaller than the amount of poweravailable, the process proceeds to step S908. On the other hand, if theamount of power is not equal to or smaller than the amount of poweravailable, the process proceeds to step S907.

In step S907, the power supply possibility determination unit 425transmits “invalid: excessive amount of power” through the communicationunit 423 as the inquiry result (corresponds to step S113 illustrated inFIG. 13). The inquiry result “invalid: excessive amount of power”indicates that because the amount of power included in the inquiry abouta power ID exceeds the amount of power that can be supplied from thepower supply apparatus 10 using the power ID included in the inquiryabout a power ID received in step S901, the power supply apparatus 10cannot supply power using the power ID. The power supply apparatus 10 istherefore prohibited from supplying power using the power ID.

In step S907, the power supply possibility determination unit 425 maytransmit “valid: within amount of power available” through thecommunication unit 423 as the inquiry result (not illustrated). Theinquiry result “valid: within amount of power available” indicates thatthe power supply apparatus 10 may supply an amount of power that can besupplied from the power supply apparatus 10 using the power ID includedin the inquiry about a power ID received in step S901 (that is, powerthat does not cause a charging process) and that is equal to or smallerthan the amount of power available.

In step S908, the power supply possibility determination unit 425transmits “valid” through the communication unit 423 as the inquiryresult (corresponds to step S113 illustrated in FIG. 13). The inquiryresult “valid” indicates that the power supply apparatus 10 can supplypower using the power ID included in the inquiry about a power IDreceived in step S901.

As a result of the above process, the power management apparatus 41 canappropriately respond to the inquiry about the power ID from the powersupply apparatus 10.

FIG. 20 is a flowchart illustrating the process for updating the amountof surplus power used performed by the power management apparatus 41according to the present embodiment. The flowchart of FIG. 20illustrates the processing performed by the power management apparatus41 in step S14 illustrated in FIG. 12.

In step S1001, the surplus power use history management unit 426 of thepower management apparatus 41 receives a power supply report through thecommunication unit 423. The power supply report includes a power ID andthe amount of power supplied by the power supply apparatus 10 using thepower ID. The power supply report is transmitted from the power supplyapparatus 10 (step S115 illustrated in FIG. 13).

In step S1002, the surplus power use history management unit 426 updatesthe amount of power available corresponding to the power ID bysubtracting the amount of power included in the power supply reportreceived in step S1001 from the amount of power available stored in thepower ID management table T20.

In step S1003, the surplus power use history management unit 426registers the amount of power included in the power supply reportreceived in step S1001 to the surplus power use information table T30 asthe amount of power supplied.

As a result of the above process, the power management apparatus 41updates various pieces of information on the basis of the received powersupply report.

FIG. 21 is a flowchart illustrating the process for calculating anelectricity bill in the settlement process according to the presentembodiment.

In step S1101, the settlement process unit 427 of the power managementapparatus 41 calculates a price A corresponding to the amount of powerpurchased a in the home 20 of the user U1. The amount of power purchaseda is obtained from the amount of power indicated by the meter 25, thatis, the amount of power purchased a is an accumulated value of theamount of power purchased stored in the power information managementtable T40 over a certain period.

In step S1102, the settlement process unit 427 calculates the amount ofpower sold b. The amount of power sold b is obtained from the amount ofpower indicated by the meter 23, that is, the amount of power sold b isan accumulated value of the amount of power sold stored in the powerinformation management table T40 over the certain period.

In step S1103, the settlement process unit 427 calculates the amount ofsurplus power used c. The amount of surplus power used c is, in thesurplus power, the amount of power supplied from the power supplyapparatus 10, that is, the amount of surplus power used c is anaccumulated value of the amount of surplus power supplied stored in thepower supply apparatus use information table T50 over the certainperiod.

In step S1104, the settlement process unit 427 calculates a price Dcorresponding to the amount of power purchased d from the power supplyapparatus 10. The amount of power purchased d indicates the amount ofgrid power supplied from the power supply apparatus 10, that is, theamount of power purchased d is an accumulated value of the amount ofgrid power supplied stored in the power supply apparatus use informationtable T50 over the certain period.

In step S1105, the settlement process unit 427 calculates an electricitybill using the following expression 1 on the basis of the prices A andD, the amount of power sold b, and the amount of surplus power used ccalculated in steps S1101 to S1104.

Electricity bill=A+(b−c)×unit price of power sold+D  (1)

After step S1105, the settlement process unit 427 asks the user U1 topay the electricity bill.

As a result of the above process, the power management apparatus 41settles the electricity bill after calculating the electricity bill forthe user U1.

As described above, in the power management system 1 according to thepresent embodiment, surplus power caused in a home of a user (consumer)is supplied to the power system (reverse flow) whereas the user canreceive power from the power system at a place different from the user'shome. As a result, the user can not only sell the surplus power but alsoreceive power corresponding to the surplus power at another place. Thepower management system 1 can thus make wider use of surplus power.

Second Embodiment

In a second embodiment, a power management system will be describedcapable of making wider use of surplus power caused in a user's home byconsuming the surplus power for a person different from the user at aplace different from the user's home. In the following description, theuser will be referred to as a “user U1”, and the person different fromthe user will be referred to as a “user U2”.

In the present embodiment, the same components as those according to thefirst embodiment are given the same reference numerals, and detaileddescription thereof is omitted.

First, a case in which the power management system according to thepresent embodiment manages power will be described while taking anexample. The power management performed by the power management systemaccording to the present embodiment, however, is not limited to thisexample.

Both the user U1 and the user U2 use a social networking service (SNS)sites on the Internet. A power generation apparatus is installed in thehome 20 of the user U1 and is generating power. The user U2 is onhis/her travels and driving an EV. When the user U1 likes content postedon the SNS site by the user U2 during the travel, the user U1 desires toprovide surplus power caused in the home thereof for the user U2. Theuser U2 stops at a rest area in which a power supply apparatus isinstalled and charges the EV. The power management system performsmanagement such that the surplus power caused in the home 20 of the userU1 offsets the power supplied to the EV of the user U2 from the powersupply apparatus. The power management system that manages power in thismanner will be specifically described hereinafter.

FIG. 22 is an overview of the configuration of a power management systemaccording to the present embodiment. FIG. 23 is a block diagramillustrating the configuration of the power management system 2according to the present embodiment. The power management system 2 willbe described with reference to these drawings.

In the power management system 2, there are two users, namely the userU1 and the user U2. The power management system 2 is different from thepower management system 1 according to the first embodiment in that theuser (user U1) who owns a power generation apparatus at home and theuser (user U2) who receives power from a power supply apparatus aredifferent from each other.

The power generation apparatus 21, the load apparatus 22, and the meter23 are installed in the home 20 of the user U1. The user U1 owns thecommunication terminal 31. The user U1 may stay at the home 20 thereof,or may stay outside the home 20.

The user U2 stays near the power supply apparatus 10. The user U2 owns acommunication terminal 35 and a load apparatus 36. The communicationterminal 35 and the load apparatus 36 have the same functions as thecommunication terminal 31 and the load apparatus 32, respectively,according to the first embodiment.

FIG. 24 is a first sequence diagram illustrating transmission ofinformation in the power management system 2 according to the presentembodiment. A process performed by the power management system 2 will bedescribed with reference to FIG. 24. Detailed description of the sameprocessing steps as those for the power management system 1 according tothe first embodiment is omitted.

In steps S101 to S105, the communication terminal 31 inquires about thepossibility of power supply and receives a power ID.

In step S206, the communication terminal 31 transmits the power ID tothe communication terminal 35. The power ID transmitted here is onegiven to the surplus power caused in the home 20 of the user U1. Sincethe communication terminal 31 transmits the power ID to thecommunication terminal 35, the user U2 can use the surplus power causedin the home 20 of the user U1.

After the communication terminal 31 transmits the power ID to thecommunication terminal 35, the power ID held by the communicationterminal 31 may be deleted. In doing so, the communication terminal 31(user U1) can be prohibited from supplying power to the load apparatus22 from the power supply apparatus 10 using the power ID. That is, thepower ID can be appropriately transferred or moved from the user U1 tothe user U2.

When transmitting the power ID to the communication terminal 35, thecommunication terminal 31 may generate a new power ID (also referred toas a “second power ID” or “second identification information”)associated with the power ID (also referred to as a “first power ID”)and transmit the generated second power ID to the communication terminal35. In this case, the power management apparatus 41 invalidates thefirst power ID. In doing so, the communication terminal 35 (user U2) isallowed to supply power to the load apparatus 36 using the second powerID, whereas the communication terminal 31 (user U1) is prohibited fromsupplying power to the load apparatus 22. In this method, too, the powerID can be appropriately transferred or moved from the user U1 to theuser U2.

In step 3211, the communication terminal 35 transmits a power supplyrequest to the power supply apparatus 10. The power supply requestincludes the power ID transmitted from the communication terminal 31 instep S206 and the amount of power to be used, which is the amount ofpower that the user U2 desires to receive.

In steps S112 and S113, an inquiry about the power ID obtained from thepower supply request in step S211 is made.

In step 3214, the power supply apparatus 10 supplies power to the loadapparatus 36 connected thereto.

Although the communication terminal 31 transmits the power ID to thecommunication terminal 35 in step S206 after the power managementapparatus 41 transmits the power ID to the communication terminal 31 instep 3105 in the above description, the power management apparatus 41may transmit the power ID to the communication terminal 35, instead. Indoing so, the communication terminal 35 can obtain the power ID withoutusing the communication terminal 31, which increases usability.

As described above, according to the power management system 2, if thecommunication terminal 31 transmits a power ID and an accumulated valueof the amount of surplus power to the communication terminal 35, whichis used by the user U2, and the communication terminal 35 transmits, tothe power supply apparatus 10, a second power supply request indicatingthat the user U2 desires to receive power with the load apparatus 36,which is used by the user U2 and different from the load apparatus 32,the power supply apparatus 10 supplies an amount of first power equal toor smaller than the amount of surplus power to the load apparatus 36 aspower that does not cause a charging process.

If the first power ID and the temporary second power ID, which isdifferent from the first power ID, are issued and associated with anaccumulated value of the amount of surplus power in a time period inaccordance with the inquiry about the possibility of power supply, thefirst power ID, the second power ID, and the accumulated value of theamount of surplus power in the time period are transmitted to thecommunication terminal 31, the communication terminal 31 transmits thesecond power ID and the accumulated value of the amount of surplus powerto the communication terminal 35 used by the user U2, the communicationterminal 35 transmits, to the power supply apparatus 10, a second powersupply request indicating that the user U2 desires to receive power withthe load apparatus 36, which is used by the user U2 and different fromthe load apparatus 32, and the power supply apparatus 10 supplies anamount of first power equal to or smaller than the amount of surpluspower to the load apparatus 36 as power that does not cause a chargingprocess, the first power is prohibited from being supplied to the loadapparatus 32.

As a result, it is possible to make wider use of surplus power caused ina home of a user by consuming the surplus power for a person differentfrom the user at a place different from the user's home.

Third Embodiment

In a third embodiment, a power management system will be describedcapable of making wider use of surplus power by consuming surplus powerthat will be caused in a user's home in the future for a persondifferent from the user at a place different from the user's home.

In the present embodiment, the same components as those according to thefirst or second embodiment are given the same reference numerals, anddetailed description thereof is omitted.

First, a case in which the power management system according to thepresent embodiment manages power will be described while taking anexample. Power management performed by the power management systemaccording to the present embodiment, however, is not limited to thisexample.

Although the surplus power caused in the home 20 of the user U1 isprovided for the user U2 in the second embodiment, the user U1 desiresto provide surplus power that will be caused in the home 20 of the userU1 in the future for the user U1 in the present embodiment.

The user U2 stops at a rest area in which a power supply apparatus isinstalled and charges the EV. The power management system performsmanagement such that the surplus power caused in the home 20 of the userU1 in a time period in which the EV is charged offsets the powersupplied to the EV of the user U2 from the power supply apparatus. Thepower management system that manages power in this manner will bespecifically described hereinafter.

The configuration of the power management system according to thepresent embodiment is the same as that of the power management system 2according to the second embodiment.

FIG. 25 is a first sequence diagram illustrating transmission ofinformation in the power management system in the present embodiment. Aprocess performed by the power management system according to thepresent embodiment will be described with reference to FIG. 25.

In step S301, the communication terminal 31 reserves a right to usesurplus power. The right to use surplus power is a right to use surpluspower that will be caused in the future. Since the user U1 reserves theright to use surplus power using the communication terminal 31, theright to use surplus power that will be caused by the power generationapparatus 21 can be defined. When reserving the right to use surpluspower, the communication terminal 31 transmits a contract ID and theamount of power requested to the power management apparatus 41. Theamount of power requested is the amount power requested to be used inthe future.

A time limit may be provided for the surplus power to be used. That is,in the surplus power caused in the future, the user U1 may receive aright to use only surplus power caused in a certain time period.Alternatively, the user U1 may receive a right to use only surplus powercaused in time periods other than a certain time period. In this case,the user U1 specifies the certain time period in step S301.

In step S302, the power management apparatus 41 gives a power ID toreserved power. The power management apparatus 41 gives the power ID topower corresponding to the amount of power requested included in thereservation of the right to use surplus power received in step S301. Thepower corresponding to the amount of power requested is the surpluspower that will be caused in the future.

If the certain time period is specified in step S301, the powermanagement apparatus 41 gives a power ID to surplus power that will becaused in the specified certain time period or surplus power that willbe caused in the time periods other than the specified certain timeperiod.

Alternatively, the power management apparatus 41 may reserve onlysurplus power corresponding to part of the amount of power requestedspecified in step S301. More specifically, the power managementapparatus 41 determines whether to reserve surplus power correspondingto all the amount of power requested specified in step S301. If thepower management apparatus 41 determines that it is difficult to reservesurplus power corresponding to all the amount of power requested, thepower management apparatus 41 may reserve only surplus powercorresponding to part of the amount of power requested.

In step S303, the power management apparatus 41 transmits, to thecommunication terminal 31, the power ID given in step S302. At thistime, the power management apparatus 41 transmits a value indicating thereserved amount of surplus power to the communication terminal 31 as theamount of power reserved.

In step S304, the communication terminal 31 transmits, to thecommunication terminal 35 (user U2), the power ID transmitted in stepS303.

FIGS. 26 and 27 are second and third sequence diagrams illustrating thetransmission of information in the power management system according tothe present embodiment.

In step S311, the communication terminal 35 transmits a power supplyrequest to the power supply apparatus 10. The power supply requestincludes the power ID transmitted from the communication terminal 31 instep S304 and the amount of power to be used, which is the amount ofpower that the user U2 desires to receive.

In step S312, the power supply apparatus 10 inquires of the powermanagement apparatus 41 about the power ID obtained as a result of powersupply request transmitted in step S311. Step S312 is the same as stepS112 in the first embodiment.

In step S313, the power management apparatus 41 transmits an inquiryabout the amount of surplus power to the meter 23 of the home 20 of theuser U1.

In step S314, the meter 23 transmits the amount of surplus power to thepower management apparatus 41 in accordance with the inquiry about theamount of surplus power received from the power management apparatus 41in step S313.

In step S315, the power management apparatus 41 determines the amount ofactual surplus power. More specifically, the power management apparatus41 determines whether or not the amount of surplus power in the timeperiod is equal to or larger than the amount of surplus power to be usedincluded in the power supply request transmitted in step S311.

If the power management apparatus 41 determines in step S315 that theamount of surplus power is equal to or larger than the amount of powerto be used (YES in step S315), processing in steps S316 and S317 isperformed. On the other hand, if the power management apparatus 41determines in step S315 that the amount of surplus power is not equal toor larger than the amount of power to be used (that is, if the amount ofsurplus power is smaller than the amount of power to be used) (NO instep S315), processing in steps S321 to S324 illustrated in FIG. 27 isperformed.

In step S316, the power management apparatus 41 transmits, to the powersupply apparatus 10, a result of the inquiry about the power IDtransmitted in step 3312. More specifically, since the amount of surpluspower is equal to or larger than the amount of power to be used, thepower management apparatus 41 notifies the power supply apparatus 10that power may be supplied.

In step S317, the power supply apparatus 10 supplies power correspondingto the amount of power to be used to the load apparatus 36 connectedthereto.

In step S321, the power management apparatus 41 transmits, to the powersupply apparatus 10, a result of the inquiry about the power IDtransmitted in step S312. More specifically, since the amount of surpluspower is smaller than the amount of power to be used, the powermanagement apparatus 41 transmits a value indicating the amount of poweravailable to the power supply apparatus 10.

In step S322, the power supply apparatus 10 transmits, to thecommunication terminal 35, the value indicating the amount of poweravailable transmitted in step S321. The communication terminal 35displays, to the user U2, the value indicating the amount of poweravailable transmitted in step S322 and might receive, from the user U2,an instruction to receive power corresponding to the amount of poweravailable from the power supply apparatus 10.

In step S323, the communication terminal 35 transmits the instruction toreceive power to the power supply apparatus 10. The instruction toreceive power is issued if the user U2 determines in step S322 toreceive the power corresponding to the amount of power available.

In step S324, the power supply apparatus 10 supplies the powercorresponding to the amount of power available to the load apparatus 36connected thereto.

Although the power management apparatus 41 gives a power ID to reservedpower in step S302 in the above description, the power managementapparatus 41 may wait until the surplus power is actually caused,instead. In this case, the power management apparatus 41 may give apower ID to the surplus power after the surplus power is actuallycaused, and transmit the power ID to the communication terminal 31. Indoing so, upon receiving the power ID in step S304, the communicationterminal 35 can instruct the power supply apparatus 10 to supply thepower to the load apparatus 36 on the basis of the actual surplus power.

Although the communication terminal 31 reserves a right to use surpluspower using the contract ID and the amount of power requested in stepS301 in the above description, the communication terminal 31 may alsouse specification information for specifying the user U2. In this case,after the surplus power is actually caused, the power managementapparatus 41 can give a power ID to the surplus power and transmit thepower ID to the communication terminal 35. In doing so, thecommunication terminal 35 can obtain the power ID without using thecommunication terminal 31 and instruct the power supply apparatus 10 tosupply power to the load apparatus 36 on the basis of the actual surpluspower.

Modifications of Embodiments

The power management system according to each of the above embodimentscan be implemented in the following manner.

FIG. 28 is a block diagram illustrating another example of theconfiguration of the power management system according to each of theabove embodiments.

A power management system 3 includes a power generation apparatusconnected to a power system, a power supply apparatus connected to thepower system, and a load apparatus connected to the power supplyapparatus. As illustrated in FIG. 28, the power management system 3includes an identification unit 41A that identifies surplus power, whichis, in power generated by the power generation apparatus, power suppliedto the power system, a generation unit 41B that generates firstidentification information associated with the surplus power, and thepower supply unit 12 that supplies an amount of first power equal to orsmaller than the amount of surplus power associated with the firstidentification information from the power system to the load apparatusthrough the power supply apparatus holding the first identificationinformation.

FIG. 29 is a flowchart illustrating a power management method performedby the power management system according to each of the aboveembodiments.

In step S1301, surplus power, which is, in the power generated by thepower generation apparatus, power supplied to the power system, isidentified.

In step S1302, the first identification information to be associatedwith the surplus power is generated.

In step 31303, an amount of first power equal to or smaller than theamount of surplus power associated with the first identificationinformation is supplied from the power system to the load apparatusthrough the power supply apparatus holding the first identificationinformation.

The components in each of the above embodiments may be configured bydedicated hardware or by executing a software program suitable for thecomponents. Alternatively, the components may be realized by a programexecution unit such as a central processing unit (CPU) or a processorthat reads and executes a software program recorded on a recordingmedium such as a hard disk or a semiconductor memory. A software programthat realizes the power management system according to each of the aboveembodiments or the like is as follows.

That is, the software program is the program stored in a non-transitorycomputer-readable recording medium storing a program for causing acomputer to implement a power management method used in a powermanagement system including a power generation apparatus correspondingto first user identification information, a first load apparatus used bya user corresponding to the first user identification information, and apower supply apparatus capable of supplying power to the first loadapparatus and installed in a place different from the power generationapparatus. The method includes receiving, from a meter that measures theamount of surplus power, which is, in power generated by the powergeneration apparatus, power supplied from the power generation apparatusto a power system, a surplus power value indicating the amount ofsurplus power, receiving, from a first communication terminal used bythe user corresponding to the first user identification information, aninquiry about power supply in which the surplus power is used in a firsttime period that lasts a certain unit time, the inquiry being associatedwith the first user identification information, issuing, in accordancewith the inquiry, first power identification information for validatingpower supply performed by the power supply apparatus using the surpluspower corresponding to the first time period for an accumulated value ofthe amount of surplus power corresponding to the first time period,transmitting the first power identification information and theaccumulated value of the amount of surplus power corresponding to thefirst time period to the first communication terminal, and causing thepower supply apparatus that has received a first power supply request,which is associated with the first power identification information,indicating that power is to be supplied to the first load apparatus tosupply an amount of first power equal to or smaller than the amount ofsurplus power to the first load apparatus as power that does not cause acharging process.

That is, the software program may be the program stored in acomputer-readable recording medium storing a program for causing acomputer to implement a power management method used in a powermanagement system including a power generation apparatus connected to apower system and a power supply apparatus that is connected to the powersystem and that supplies power to a load apparatus. The method includesidentifying surplus power, which is, in power generated by the powergeneration apparatus, power to be supplied to the power system,generating first identification information to be associated with thesurplus power, and supplying an amount of first power equal to orsmaller than the amount of surplus power associated with the firstidentification information from the power system to the load apparatusthrough the power supply apparatus that has obtained the generated firstidentification information.

Part or all of the above embodiments can be described as follows, butare not limited to the following description.

(1) A power management method used in a power management systemincluding a power generation apparatus connected to a power system and apower supply apparatus that is connected to the power system and thatsupplies power to a load apparatus includes identifying surplus power,which is, in power generated by the power generation apparatus, powersupplied to the power system, generating first identificationinformation to be associated with the surplus power, and supplying anamount of first power equal to or smaller than the amount of surpluspower associated with the first identification information from thepower system to the load apparatus through the power supply apparatusthat has obtained the generated first identification information.

(2) In the method according to (1), if the power supply apparatus hasnot obtained the first identification information, second power thatcauses a charging process may be supplied from the power system to theload apparatus through the power supply apparatus, and if the powersupply apparatus has obtained the first identification information, thefirst power that does not cause a charging process may be supplied tothe load apparatus.

(3) In the method according to (2), the power supply apparatus mayinclude a receiver used for paying money for the supplied power. Themethod may further include receiving money using the receiver if thesecond power has been supplied and not receiving money using thereceiver if the first power has been supplied.

(4) The method according to any of (1) to (3) may further includeperforming, if the surplus power is supplied to the power system, aprocess for providing a price corresponding to the amount of surpluspower. If the first power has been supplied, a process for providing aprice corresponding to the amount of power obtained by subtracting theamount of first power from the amount of surplus power may be performedin the provision process.

(5) The method according to any of (1) to (4) may further includetransmitting the first identification information to a firstcommunication terminal of a first user, who owns the power generationapparatus, and, if the first communication terminal transmits, to thepower supply apparatus using the first identification information, arequest indicating that power is to be supplied from the power supplyapparatus, supplying the first power to the load apparatus.

(6) The method according to (5) may further include transmitting thefirst identification information from the first communication terminalto a second communication terminal of a second user, who is differentfrom the first user who owns the power generation apparatus, and, if thesecond communication terminal transmits, to the power supply apparatususing the first identification information, a request indicating thatpower is to be supplied from the power supply apparatus, supplying thefirst power to the load apparatus.

(7) In the method according to (6), if the first identificationinformation is transmitted, the first identification information held bythe first communication terminal may be deleted after the firstidentification information is transmitted.

(8) The method according to (6) may further include generating, if thefirst identification information is transmitted, second identificationinformation associated with the first identification information butdifferent from the first identification information, transmitting thegenerated second identification information from the first communicationterminal to the second communication terminal, supplying the first powerfrom the power system to the load apparatus through the power supplyapparatus that has obtained the second identification information, andprohibiting the power supply apparatus that has obtained the firstidentification information from supplying the first power.

(9) In the method according to (8), if the first identificationinformation is generated before the identified surplus power is actuallycaused, the generated first identification information may betransmitted to the second communication terminal after the surplus poweris actually caused.

(10) The method according to (6) may further include receivingspecification information for specifying the second user, and, if thefirst identification information is generated before the identifiedsurplus power is actually caused, transmitting the generated firstidentification information to the communication terminal of the seconduser specified by the specification information after the surplus poweris actually caused.

(11) In the method according to any of (1) to (10), in the powermanagement system, power supply-demand balance may be adjusted in eachtime period, and the power supply apparatus may supply the first powerin the same time period in which the power generation apparatus suppliesthe surplus power to the power system.

(12) The method according to any of (1) to (11) may further includemeasuring, in the power generated by the power generation apparatus in aperiod from a start of a time period including a first time to the firsttime, power supplied to the power system, identifying the measured poweras the surplus power, and supplying an amount of first power equal to orsmaller than the amount of surplus power to the load apparatus.

(13) The method according to (12) may further include identifying powerobtained by adding estimated surplus power, which is, in power estimatedto be generated by the power generation apparatus in a period from thefirst time to an end of the time period, power estimated to be suppliedto the power system, to the surplus power as new surplus power, andsupplying an amount of first power equal to or smaller than the amountof new surplus power to the load apparatus.

(14) A power management system including a power generation apparatusconnected to a power system and a power supply apparatus that isconnected to the power system and that supplies power to a loadapparatus includes an identifier that identifies surplus power, whichis, in power generated by the power generation apparatus, power suppliedto the power system, a generator that generates first identificationinformation to be associated with the surplus power, and a powersupplier that supplies an amount of first power equal to or smaller thanthe amount of surplus power associated with the first identificationinformation from the power system to the load apparatus through thepower supply apparatus that has obtained the generated firstidentification information.

According to (1), in the power management system, the surplus powercaused in a home of a user (consumer) is supplied to the power system(reverse flow) whereas the power system supplies power at a placedifferent from the users home. As a result, the user can not only sellthe surplus power but also receive an amount of power corresponding tothe amount of surplus power at another place. The power managementsystem can thus make wider use of surplus power.

According to (2), in the power management system, the user need not payfor the power supplied from the power supply apparatus. Since the powermanagement system performs management such that the surplus poweroffsets the power supplied from the power supply apparatus, the userneed not pay for the power supplied from the power supply apparatus. Theuser can therefore make wider use of surplus power without paying extramoney.

According to (3), the power management system does not receive moneycorresponding to the power supplied from the power supply apparatus.Since the power management system performs management such that thesurplus power offsets the power supplied from the power supplyapparatus, the power management system does not receive the moneycorresponding to the power supplied from the power supply apparatus. Theuser can therefore make wider use of surplus power without paying extramoney.

According to (4), the power management system provides, for the user, aprice corresponding to the amount of power obtained by subtracting theamount of power supplied from the power supply apparatus from the amountof surplus power. The user can therefore make wider use of surplus powerwithout paying extra money.

According to (5) the power management system supplies power to the loadapparatus after the first identification information is input to thepower supply apparatus. The user can supply power to the load apparatusby inputting the first identification information to the power supplyapparatus. In doing so, the user can intuitively understand a time tosupply power to the load apparatus, which improves usability.

According to (6), in the power management system, the surplus powercaused in a home of a user (first user) is supplied to the power system(reverse flow) whereas a user (second user) who does not own a powergeneration apparatus can receive power from the power system. As aresult, even users who do not own a power generation apparatus can usesurplus power.

According to (7), the power management system can prohibit the firstuser from making the power supply apparatus supply power to his/her loadapparatus using the first identification information after the firstuser transmits the first identification information to the second user.That is, the power management system can appropriately transfer or movethe identification information from the first user to the second user.

According to (8), in the power management system, the second user isallowed to supply power to his/her load apparatus using the secondidentification information whereas the first user is prohibited fromsupplying power to his/her load apparatus. That is, the power managementsystem can appropriately transfer or move the identification informationfrom the first user to the second user.

According to (9), the communication terminal that has received theidentification information can supply power from the power supplyapparatus to the load apparatus on the basis of the actual surpluspower.

According to (10), the communication terminal that has received theidentification information can obtain the identification informationwithout using another communication terminal and supply power from thepower supply apparatus to the load apparatus on the basis of the actualsurplus power.

According to (11), the power management system can supply power to theload apparatus without disrupting the supply-demand balance in the timeperiod. As a result, it is possible to avoid increasing a powerprocurement cost of a retailer.

According to (12), in the power management system, an amount of powercorresponding to the amount of surplus power actually caused in the timeperiod can be supplied to the load apparatus. As a result, it ispossible to avoid increasing the power procurement cost of the retailer.

According to (13), in the power management system, the sum of the amountof surplus power actually caused in the time period and the amount ofsurplus power estimated to be caused in the time period can be suppliedto the load apparatus. As a result, it is possible to avoid increasingthe power procurement cost of a retailer.

According to (14), the same advantageous effects as above can beproduced.

Although power management systems according to one or a plurality ofaspects and the like have been described on the basis of embodiments,the present disclosure is not limited to these embodiments. The one orplurality of aspects may include modes obtained by modifying the aboveembodiments in manners that can be conceived by those skilled in the artor modes obtained by combining components in different embodiments,insofar as such modes do not deviate from the scope of the presentdisclosure.

The present disclosure can be used for a power management system capableof making wider use of surplus power.

What is claimed is:
 1. A power management method used in a powermanagement system including a power generation apparatus correspondingto first user identification information, a first load used by a usercorresponding to the first user identification information, and a powersupply apparatus capable of supplying power to the first load, themethod comprising: receiving a surplus power value, indicating an amountof surplus power supplied from the power generation apparatus to a powersystem; receiving, from a first communication terminal used by the usercorresponding to the first user identification information, an inquiryregarding a power supply using the surplus power in a first time periodthat lasts for a predetermined unit time, the inquiry being associatedwith the first user identification information; issuing, in accordancewith the inquiry, first power identification information for allowingthe power supply apparatus to supply power using the surplus powercorresponding to the first time period, in association with anaccumulated value of the amount of surplus power corresponding to thefirst time period; transmitting the first power identificationinformation and the accumulated value of the amount of surplus powercorresponding to the first time period, to the first communicationterminal; and causing the power supply apparatus that has received afirst power supply request, to supply an amount of power equal to orsmaller than the accumulated value of the amount of surplus power, tothe first load, as first power that does not cause a fee chargingprocess, the first power supply request being associated with the firstpower identification information and requesting a power supply to thefirst load.
 2. The method according to claim 1, wherein the first powersupply request is input from the first communication terminal to thepower supply apparatus.
 3. The method according to claim 1, wherein thesurplus power value is periodically received from a meter, and wherein,after the inquiry is received, surplus power values are accumulated froma start of the first time period including a reception time, at whichthe inquiry has been received, to the reception time, to generate theaccumulated value of the amount of surplus power corresponding to thefirst time period.
 4. The method according to claim 1, wherein, afterthe inquiry is received, a meter is requested to output surplus powervalues corresponding to the first time period including a receptiontime, at which the inquiry has been received, and wherein, after thesurplus power values corresponding to the first time period are receivedfrom the meter, the surplus power values corresponding to the first timeperiod are accumulated to generate the accumulated value of the amountof surplus power corresponding to the first time period.
 5. The methodaccording to claim 1, wherein the first power supply request includes anamount of power to be supplied to the first load.
 6. The methodaccording to claim 1, wherein, when the accumulated value of the amountof surplus power corresponding to the first time period is equal to orsmaller than a predetermined minimum value, the first poweridentification information is not issued in association with theaccumulated value of the amount of surplus power corresponding to thefirst time period.
 7. The method according to claim 1, wherein, when theaccumulated value of the amount of surplus power corresponding to thefirst time period is equal to or smaller than a predetermined minimumvalue, the first power identification information and the accumulatedvalue are not transmitted to the first communication terminal inaccordance with the inquiry.
 8. The method according to claim 1,wherein, when the accumulated value of the amount of surplus powercorresponding to the first time period is equal to or smaller than apredetermined minimum value, a notification indicating that theaccumulated value of the amount of surplus power corresponding to thefirst time period is equal to or smaller than the predetermined minimumvalue is transmitted to the first communication terminal in accordancewith the inquiry.
 9. The method according to claim 1, furthercomprising: receiving, from the power supply apparatus, an inquiryrequest including an amount of power to be supplied to the first load;and outputting, when the amount of power included in the inquiry requestexceeds the accumulated value of the amount of surplus powercorresponding to the first time period, an instruction to prohibit thepower supply apparatus from supplying power to the first load.
 10. Themethod according to claim 1, further comprising: receiving, from thepower supply apparatus, an inquiry request including an amount of powerto be supplied to the first load; and causing, when the amount of powerincluded in the inquiry request exceeds the accumulated value of theamount of surplus power corresponding to the first time period, thepower generation apparatus to supply the amount of power equal to theaccumulated value of the amount of surplus power corresponding to thefirst time period, to the first load as the first power that does notcause a fee charging process.
 11. The method according to claim 1,wherein, after the first time period ends, the power supply apparatus isstopped from supplying power using the surplus power corresponding tothe first time period on the basis of the first power identificationinformation.
 12. The method according to claim 1, wherein the powermanagement system further includes a second load, which is differentfrom the first load, and wherein power obtained by subtracting powerused by the second load from power generated by the power generationapparatus is determined as the surplus power.
 13. The method accordingto claim 1, wherein, when the power generation apparatus has notobtained the first power identification information, the power supplyapparatus supplies second power that causes a fee charging process, tothe first load.
 14. The method according to claim 13, wherein the powersupply apparatus includes a receiver used for a process of paying moneyfor supplied power, the method further comprising: when the power supplydevice has supplied the second power to the first bad, causing thereceiver to accept the process of paying money; and when the powersupply device has supplied the first power to the first load,prohibiting the receiver from performing the process of paying money.15. The method according to claim 1, further comprising: calculating aprice corresponding to the amount of surplus power, wherein, in thecalculating, when the power supply apparatus has supplied the firstpower to the first load, a price corresponding to an amount of powerobtained by subtracting an amount of the supplied first power from theaccumulated value of the amount of surplus power is calculated.
 16. Themethod according to claim 1, wherein the first communication terminaltransmits the first power identification information and the accumulatedvalue of the amount of surplus power corresponding to the first timeperiod, to a second communication terminal used by a user correspondingto second user identification information different from the first useridentification information, and wherein, when the second communicationterminal has transmitted, to the power supply apparatus, a second powersupply request requesting a power supply to a second load, which is usedby the user corresponding to the second user identification informationand is different from the first load, the power supply apparatussupplies an amount of power equal to or smaller than the amount ofsurplus power, to the second load, as the first power that does notcause a fee charging process.
 17. The method according to claim 1,wherein the first power identification information and temporary secondpower identification information different from the first poweridentification information are associated with the accumulated value ofthe amount of surplus power corresponding to the first time period andare issued in accordance with the inquiry, wherein the first poweridentification information, the second power identification information,and the accumulated value of the amount of surplus power correspondingto the first time period are transmitted to the first communicationterminal, wherein the first communication terminal transmits the secondpower identification information and the accumulated value of the amountof surplus power to a second communication terminal used by a usercorresponding to second user identification information different fromthe first user identification information, wherein the secondcommunication terminal transmits, to the power supply apparatus, asecond power supply request requesting a power supply to a second load,which is used by the user corresponding to the second useridentification information and is different from the first load, andwherein, when the power supply apparatus has supplied an amount of powerequal to or smaller than the amount of surplus power, to the secondload, as the first power that does not cause a fee charging process, thepower supply apparatus is prohibited from supplying the first power tothe first load.
 18. The method according to claim 1, wherein theaccumulated value of the amount of surplus power corresponding to thefirst time period includes a value obtained by adding surplus powervalues corresponding to a period from a start of the first time periodincluding a reception time, at which the inquiry has been received, tothe reception time, to an estimated accumulated value of the amount ofsurplus power from the reception time to an end of the first timeperiod.
 19. A power management system comprising: a power generationapparatus corresponding to first user identification information; afirst load used by a user corresponding to the first user identificationinformation; a power supply apparatus capable of supplying power to thefirst load; one or more memories; and circuitry operative to: receive asurplus power value, indicating an amount of surplus power supplied fromthe power generation apparatus to a power system; receive, from a firstcommunication terminal used by the user corresponding to the first useridentification information, an inquiry regarding a power supply usingthe surplus power in a first time period that lasts for a predeterminedunit time, the inquiry being associated with the first useridentification information; issue, in accordance with the inquiry, firstpower identification information for allowing the power supply apparatusto supply power using the surplus power corresponding to the first timeperiod, in association with an accumulated value of the amount ofsurplus power corresponding to the first time period; transmit the firstpower identification information and the accumulated value of the amountof surplus power corresponding to the first time period, to the firstcommunication terminal; and cause the power supply apparatus that hasreceived, from the first communication terminal, a first power supplyrequest, to supply an amount of power equal to or smaller than theaccumulated value of the amount of surplus power, to the first load, asfirst power that does not cause a fee charging process, the first powersupply request being associated with the first power identificationinformation and requesting a power supply to the first load.
 20. A powermanagement method comprising: receiving a surplus power value,indicating an amount of surplus power supplied from a power generationapparatus to a power system; receiving an inquiry regarding a powersupply using the surplus power in a first time period, the inquiry beingassociated with first user identification information; issuing, inaccordance with the inquiry, first power identification information forallowing a power supply apparatus to supply power using the surpluspower corresponding to the first time period, in association with anaccumulated value of the amount of surplus power corresponding to thefirst time period; receiving a first power supply request, which isassociated with the first power identification information, and requestsa power supply to a first load; and causing the power supply apparatusto supply an amount of power equal to or smaller than the accumulatedvalue of the amount of surplus power, to the first load, as first powerthat does not cause a fee charging process.